The brothers who blew themselves up in Brussels are the latest in a long line of terrorist siblings.
Mia Bloom, professor at Georgia State University, told INSIDE EDITION: "These high risk missions require a great deal of trust and commitment. Trust and commitment is a plan that fulfills instantly when it is with a member of your family."
Last week, Belgium police arrested Salah Abdeslam for his role in the November attacks in Paris. His brother was behind that atrocity, blowing himself up at a cafe.
"ISIS has gone to great lengths to recruit entire families. Thirty percent or one-third of the foreign fighters that have gone to ISIS have some sort of family connection," Bloom said.
Going back to the Sept. 11, 2001 terror attacks, terrorist siblings have been responsible for attacks; six of the 19 hijackers on 9/11 were brothers.
But the most infamous sibling terrorists of all are the Tsarnaev brothers, who were responsible for the Boston Marathon bombing in 2013.
Now, experts are wondering if trained behavior analysts should be roaming our airports looking for suspicious travelers.
None of the three men from the Brussels airport attack were spotted with carry-on luggage.
"There are profile indicators that would determine some sort of suspicious activity that we have to address," former NYPD Commissioner Bernard Kerik told IE, saying that sharp eyed analysts may have been able to prevent the terrorist attacks.
See images of memorials in Brussels: