Sibling psychology might have been the motivating force behind the Boston Marathon attack, a new study has revealed.

The brothers, Tamerlan and Dzhokhar Tsarnaev who have been the chief suspects for the Boston bombings are not the only siblings who have committed crimes together in history, the CBS News reports.

According to the report, the attacks on September 11, 2001 had also been prompted by the three brothers, Osama Bin Laden, Khalid Sheikh Mohammad, and Mohammed Atef, where Osama was the mastermind, Khalid Sheikh Mohammad is believed to be the planner and Atef was the one who organized the hijackers.

Time magazine science editor Jeffrey Kluger said that children are influenced by the place and environment they are born into and the elder brother always acts as the mentor to his younger siblings.