Sibling rivalries just got more controversial from new research that has revealed that second-born children are more likely to become criminals than first-born kids.

The research found that second-born children are more likely to be troublesome, whether they have issues with authority at school or problems with violating the law.

Researchers from the University of Florida, Northwestern University, and MIT all teamed up to carry out a study of the lives of thousands of sets of brothers. The brothers all came from either Florida or Denmark, meaning that they came from two countries that have very different cultural behaviors. Despite this, the findings were similar.

The study concluded that the second-born brothers in Florida and Denmark were more likely to defy authority than their older brothers.

 “Despite large differences in environments across the two areas, we find remarkably consistent results: In families with two or more children, second-born boys are on the order of 20 to 40 percent more likely to be disciplined in school and enter the criminal justice system compared to first-born boys even when we compare siblings,” the researchers said.

The researchers believe that their findings are the result of early child-rearing. They explained that second-born children have less one-on-one attention from their parents and are not watched quite as closely as a first-born. Second-born children then act recklessly to get more parental attention, researchers theorize.

On top of that, the researchers noted that parents often take more time off from work with a first-born child when they are born. Once they have their second child, they return to work much faster typically. Second-born children also look to their older sibling as a role model for how to behave, while first-born kids look to their parents to see how to behave. This means that second-born children have a less mature role model than their older siblings.

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