The presence of a child carries happiness and blessings to other siblings. This stigma is mostly believed in by the widespread catchphrase "more children, more fortune" which remains echoed in society. Through this slogan, many people infer that the presence of a "second child" or so on can be translated as a "playmate" for his siblings in the future. However, children unequivocally have their own experiences regarding relationships with other brothers or sisters. The relationship, in this case, may refer to positive or negative. One of the negative relationships that may ensue is sibling rivalry in the family. According to (Shaffer & Kipp, 2014), sibling rivalry refers to the competition, jealousy, and animosity between siblings that arise following the birth of a younger child. The conflict between siblings occurs because the birth and presence of a new the love, affection, and praise that were initially intended exclusively for them to be shared with their sibling. Besides, sibling rivalry can initiate from younger siblings to older siblings due to the fear of losing the attention and affection of parents (Ulia, 2020). Several factors influence sibling rivalry, namely: 1) parents do not treat children equally; 2) adjacent birth order; 3) same gender; 4) small age gap; 5) small number of children; 6) receiving influence from outside, such as child care by outsiders (Putri & Budiartati, 2020). Generally speaking, sibling rivalry is provoked by siblings with an age gap of 1-3 years, tends to reappear at the age of 3-5 years, and reappear more at the age of 8-12 years (Tiyaningsih, 2017). According to (Juwita, 2017), sibling rivalry can be overcome by respecting the uniqueness of each child, encouraging empathy and cooperation, making clear rules for children to follow, and teaching how to resolve a conflict.

Such a phenomenon remains an issue that is deemed trivial by society. Almost 75% of children in Indonesia, in fact, experience sibling rivalry with varying reactions (Lazdia & Kusuma, 2019), from aggressive behavior to exploding emotionally for no reason. This state of sibling rivalry is very likely to be sustained from school to adulthood. According to (Waluyo & Purwandari, 2010), the coming of sibling rivalry leads children to be aloof and become crybaby. Furthermore, sibling rivalry prompts anxiety, depression, diminished emotional control, and difficulties in adjusting, because siblings may act as a factor in mitigating problems of the environment (Buist et al., 2013). Sibling rivalry was once a motive for abuse between children in Blitar in 2018. An 18-year-old boy lacerated his brother out of revenge and jealousy (Gunawan, 2018). Likewise, the case in Bojonegoro, based on previous research conducted in Kedungadem Village, found that 7 out of 10 parents reported that their children were jealous of their siblings (Muarifah & Fitriana, 2019). Therefore, a strategy is needed to deal with ongoing circumstances.

One activity that can reduce competition is inviting children to work together, such as through cooperative games (Shalehah et al., 2018). Cooperative play is an activity related to social interaction with organized activities and a sense of group identity (Santrock, 2014). When playing, children develop their ability to interact with each other and maintain social relationships. The characteristic of cooperative games is cooperation or distribution of tasks and roles to achieve a shared goal (Subaida, 2016). Research by (Hasinuddin & Siti, 2017) discovered that cooperative games influenced conflict reactions between siblings. This significant decrease occurred after three cooperative game sessions were carried out every week in the experimental group. Corresponding research was also conducted by (Lubis, 2019), which showed that cooperative games could reduce sibling rivalry behavior in children. Research found that the forms of cooperative play were very diverse, from arranging building blocks to playing with Lego.

Cooperative games are applicable as an intervention tool aimed at increasing cooperation and coordination between siblings (Lubis, 2019). Cooperative play allows children to divide tasks and achieve goals together rather than competing. For children in Java, especially East Java and Central Java, one of the traditional cooperative games amid modernization is benthik, or what is known as gatrik. Especially in Bojonegoro, East Java, this game is played in groups using a two-on-two wooden stick, in which one wooden stick is ± 40 cm long (benthong) and the other is ± 15 cm (janak) (Said & Suyanto, 2018). Benthik benefits children both physically and mentally, including cooperation, honesty, and sportsmanship (Hidayanti, 2017). Although playing varies depending on the region, this game can easily be established as a cooperative game between siblings. However, there is very little research that uses such a game as a cooperative play medium in overcoming sibling rivalry, especially for subjects in elementary school. Therefore, this research examines benthik as a form of cooperative play that can be used as an alternative to reduce sibling rivalry among children. Apart from that, this research also contributes to reviving traditional regional games which are being replaced by gadgets.

This research used quantitative methods with a quasi-experiment approach. The experimental design used a non-equivalent control group design consisting of an experimental group and a similar comparison (control) group (Notoatmodjo, 2018). Measurements of the level of sibling rivalry were carried out before the experiment (pretest) and after the experiment (posttest) as presented in Table 1.

The research was carried out at SD Negeri 1 Sumberjo (state elementary school), Trucuk Subdistrict, Bojonegoro Regency. This site was assessed based on knowledge regarding Benthik games and many residents are still familiar with this game. Moreover, the availability of fields in villages is also more accessible than those in urban areas.

The sample for this research was students in grades 2, 3, and 4 who were included in the research subject criteria and were selected using stratified random sampling. The criteria determined are children aged 8-12 years or elementary school level, having sibling rivalry which was found through research scales, and having at least one sibling (either biological or cousin). The total research sample comprised 30 children (M age=8.6; SD age=1.037) with an average age gap between siblings of around 1 – 2 years (Table 2). Subjects involved in this research had obtained approval represented by their parents by filling out informed consent.

The instrument used in collecting primary data is the sibling rivalry scale by (Sasmita, 2020) which was prepared according to the theory of (Shaffer & Kipp, 2014). In employing pretest and posttest, the subjects were informed of the 8 scale item statements and chose a rating range ranging from very suitable to very unsuitable (according to a 4-point Likert scale). This is necessary due to the limited understanding of grade 2 children when they are only presented with a scale without any assistance from researchers to provide an overview of the meaning of each statement. Filling in the scale was carried out before (pretest) and after (posttest) cooperative play was given in the form of Benthik.

The quantitative data that had been collected through the scale was also complemented through interviews with representatives of students’ parents. In interviews, there were guidelines prepared by researchers according to the sibling rivalry aspect by (Shaffer & Kipp, 2014), namely aspects of jealousy, competition, and animosity that lead to conflict between siblings, and added one aspect that represents changes in children's attitudes after receiving intervention of Benthik and challenge with siblings. Exploration through interviews was aimed at finding out how sibling rivalry occurs between children and their siblings, as well as changes after receiving the intervention of the game.

The research module and pocketbook were prepared to ensure uniformity in how to play during data collection and it was expected that children would still be able to play Benthik even though the research was completed. The pocketbook was taken from modules that have been prepared, the difference lies in the design of the colorful pocketbook and several illustrations so it will attract children's interest and how to win the game which contains important values in Benthik. After going through the preparation stage, the module underwent expert validation, namely by a psychologist, to assess the fitness of the content and theory in the module Table 3. Based on an assessment by a psychologist, The Benthik game guide module received a final score of 96 in the very good category. Some suggestions and improvements were provided by psychologist said, in general the module has been structured systematically, but it is necessary to add the time allocation for each session on pages 6–7, so that the overall time allocation is clear and the content review is worthy of inclusion, however, with minor revisions.

The game concepts in the pocketbook and game modules are written based on the results of content analysis of the original Javanese manuscript of 1912. Benthik is played using wooden sticks, twigs, or bamboo. The players prepare two pieces from fairly hard wooden twigs, one benthik is called janak (small) because its length is ± 15 cm, and the other one is benthong (large) as it is twice the length of the small stick (janak) which is ± 40 cm (Soekardi, 1912). Generally, benthik is played on a fairly large plane such as a field and a house yard because it requires a hole smaller than janak. This game consists of two teams encompassing no less than two people. During the research, children and their siblings were grouped in the same team so they could work together. An overview of the grouping between siblings is presented in Figure 1.

This research was carried out in several stages. At the preliminary stage, a literature study was carried out through articles from reputable scientific journals, and an original Javanese manuscript from 1912 discussing the procedures for playing several traditional games, including Benthik, was obtained as well. The second phase is to develop research instruments by discovering conceptual and operational definitions, as well as aspects of sibling rivalry and cooperative play. Following that is arranging the sheet of the sibling rivalry scale by (Sasmita, 2020) which was put together according to the theory of (Shaffer & Kipp, 2014). The subsequent step is to develop interview guidelines according to sibling rivalry aspects as well as several additional questions related to the implementation of benthik. The final step is to develop research modules for facilitators and pocketbooks equipped with important values in Benthik for students and parents. The procedures for playing Benthik are adapted from the original Javanese manuscript source from 1912.

The research was carried out for two weeks with four Benthik schedules in the experimental group. Before the research proceeded, the subject's parents/guardians filled out informed consent as a form of approval. Next, the researchers conducted randomization using Microsoft Excel to determine 15 students in the experimental group and 15 students in the control group according to the subject criteria. The experimental phase began with a pretest for both groups. Then, the experimental group started Benthik games for three plays followed by interviews with several parents regarding changes in attitudes shown by children towards their siblings. During the meeting break, subjects in the experimental group were given some challenges that could be done at home with relatives. Monitoring the implementation of the challenge was also assisted by parents so that it remained well-controlled. The experiment was concluded by a posttest for both groups and the researchers provided benthik intervention to both groups simultaneously.

Processing data obtained in the field commenced by inputting the scale sheet that students had filled out during the pretest and posttest into Google Spreadsheet. Data processing was carried out by scoring student assessments on a scale sheet to determine the level of sibling rivalry. Primary data in the form of subjects' sibling rivalry scores were handled by paired sample t-test and independent sample t-test analysis using JAMOVI 2.3.16. Meanwhile, additional data in the form of verbatim interviews from several parent representatives were reduced into several themes through exploratory analysis, emergent theme analysis, and general theme analysis to examine patterns between the research problem and the subject.

The independent sample t-test analysis test on the experimental and control groups was carried out to be able to compare the sibling rivalry of the two groups after the experimental period was over. There were several assumption tests before the independent sample t-test analysis was organized, including normality and homogeneity tests.

Based on the Kolmogorov-Smirnov measurement value, p> 0.05, so the data are normally distributed. Meanwhile, the results of the homogeneity test based on Levene's value found p> 0.05, therefore, there was no difference in variance in the sibling rivalry data between the experimental and control groups (homogeneous data). Meanwhile, the descriptive analysis revealed that the experimental group (M= 14.7; SD= 4.85) had a lower mean sibling rivalry after the treatment compared to the control group (M= 19.2; SD= 4.00) (see Table 4).

The hypotheses proposed are as follows, Ho: There is no difference in sibling rivalry between the experimental group and the control group after Benthik treatment; Ha: There is a difference in sibling rivalry between the experimental group and the control group after Benthik treatment.

Based on the results of the independent sample t-test that can be seen in Figure 2, it obtained a tvalue= -2.79 with df= 28 and p= 0.009 (<0.05). The tvalue (2.79) > t table (2.048), which implies Ho is rejected and Ha is accepted. Thus, the results of the independent sample t-test analysis showed that there was a significant difference in sibling rivalry between the experimental and control groups after Benthik intervention (t[28]= -2.79; p< 0.05).

After the independent sample t-test was completed, the researchers continued the analysis using a paired sample t-test to examine the effect of Benthik on the experimental group by observing the scores before and after the intervention. The assumption test that should be carried out before the paired sample t-test analysis is the normality test using Kolmogorov-Smirnov, which found p > 0.05. It suggests that the overall data obtained were normally distributed. Meanwhile, the results of the descriptive analysis indicated that in the experimental group, the level of sibling rivalry before the game (M= 17.3; SD= 4.72) was higher than after the game (M= 14.7; SD= 4.85) (Table 5).

The hypotheses proposed are as follows, Ho: There is no difference in sibling rivalry before and after Benthik in the experimental group; Ha: There is a difference in sibling rivalry before and after benthik in the experimental group.

Based on the results of the paired samples t-test analysis comparing sibling rivalry before and after Benthik in the experimental group that can be seen in Figure 3 showed t= 2.33 (> 0.05) with df = 14 and p= 0.035 (<0.05). The calculated tvalue (2.33) > t table (2.145), which denotes Ho is rejected and Ha is accepted. Thus, it can be inferred that there was a difference in sibling rivalry before and after benthik in the experimental group.

The results of the paired sample t-test correlation analysis suggested that the contribution of benthik to the diminishing sibling rivalry was 0.570² = 0.32 (32%). Hence, it implies that 32% of the decrease in sibling rivalry occurred due to Benthik, while the remaining 68% was caused by other factors, such as the implementation of challenges and changes in interactions built with sib-lings at home. All the results of the t-test analysis show that Benthik games can lessen the level of sibling rivalry in children. Besides, the game can serve as an appropriate modification of cooperative play to overcome sibling rivalry. This is based on the values of Benthik as cooperative play which is associated with aspects of sibling rivalry among children.

To further the analysis into the realm of sibling rivalry aspects, researchers also compared sibling rivalry scores in each aspect before and after treatment in the experimental group. This is to investigate which aspects have a significant decrease after benthik with siblings. Figure 4 shows the graphic results found.

This graph indicates Benthik had a significant decrease in the aspects of competition and jealousy, while the animosity feature did not show a significant decrease. This was then explored further by researchers through secondary data collection by interviewing students' parents. The explanation regarding the ineffectiveness of Benthik in overcoming hatred was due to inadequate experiences when playing with siblings, so the experience reappeared when playing.

"But yesterday same like before, he lost (playing) with the older brother. He said that." (Inter-view P1. 22-23)

However, both aspects of sibling rivalry subsided after intervention. This decline is ex-plained further in the theme of changing attitudes towards the value of benthik which is a new finding in research.

Another finding that reinforces the value of benthik games in resolving sibling rivalry is reflected in in-depth interviews with students' parents who explain changes in attitudes after the intervention with siblings. From Table 6 several subthemes found are:

In Benthik games, children were introduced to the equality of task distribution. This value is expected to foster justice between siblings. Children can implement equal distribution of tasks well through the challenges given, namely sweeping and washing dishes with siblings.

"Yes, usually big brother sweeps (the floor), and the little brother will give command. That is the brother, and that one is the little brother." (Interview P1. 133-135)

"...the big sister usually washes dishes "Come on Lyn, put them on the dish rack" she usually helps like that." (Interview P3. 183-190)

Through an equal task distribution, there are not any objections between older and younger siblings and instead, an attitude of helping each other indirectly arises.

"Usually the older brother wants to eat anything like seblak 'Lil’ bro can you buy sausage?' we’ll eat it together" (Interview P2. 81-82)

"Sometimes he says "help me," he offers himself. I don't think they can prepare food yet, but usu-ally we eat together." (Interview P3. 193)

In the end, the values instilled by Benthik, such as cooperation, can bring siblings closer.

"Well, it's more intimate between siblings..." (Interview P3. 200-204)

These excerpts illustrate that the activity of playing with siblings is not a trivial matter if it is accompanied by relevant challenges and the most important thing is to instill values in children. This research shows results corresponding to previous research ((Hasinuddin & Siti, 2017); (Lubis, 2019); (Maimunah et al., 2022)), that cooperation has a role in reducing sibling rivalry be-havior among children. Even though there are various types of games, there are distinctive charac-teristics in cooperative play. Through cooperative games, children can discuss and plan strategies to achieve certain goals (Lubis, 2019). This characteristic can reduce competition in children. (Maimunah et al., 2022) also suggested that cooperative play can reduce disputes between siblings because each child has different roles. Therefore, through cooperative play, children will learn to work together instead of competing.

This research specifically contributes to the field of revitalizing traditional regional games among the younger generation. Through this game, schools and parents can easily introduce ben-thik games to children and make it a solution to overcome sibling rivalry amid modernization. However, there are several limitations in the research, such as there is no analysis of the positive impact of sibling rivalry on children. This could be an implication for future researchers so that they will optimize the positive side of sibling rivalry so that it contributes to a good impact on children. Apart from that, limitations in terms of selection effects were not anticipated by the researchers, where the placement of participants into experimental and control groups did not take into account confounding variables, such as differences in parenting patterns between parents. The application of Benthik games can be applied to urban populations. Considering the differences in characteristics of urban and rural communities, indeed, there are many differences in sibling rivalry reactions in children living in urban areas.

This research aims to examine the influence of traditional Benthik from East Java which can reduce sibling rivalry in children and explain how the concept of Benthik can reduce sibling rivalry in children. Using a quasiexperimental method, this research was carried out at SD Negeri 1 Sumberjo Bojonegoro (state elementary school) and involved 30 children aged 8 to 12 years old, each of whom had at least one sibling.

All research results through t-test analysis and thematic tests suggest that benthik games can lessen the level of sibling rivalry in children. Through paired sample t-test analysis, it indicates a significant effect of Benthik on the condition of sibling rivalry in children, with a p-value of 0.035 (<0.05), thus implying that modified benthik has the potential to be an effective intervention to overcome sibling rivalry.

It should be emphasized that playing with siblings is not a trivial matter if it is accompanied by relevant challenges and the most important aspect is to instill values in children. This research contributes to the development of research in the field of child development and traditional games for children.