Siblings profoundly affect each other’s lives — for better or worse. Get this: Siblings who report feeling close to one another tend to either both graduate college or both drop out, as a unit. So why are sibling relationships so impactful? Because they’re rarely neutral. Brothers and sisters have strong feelings toward one another, sometimes positive, sometimes negative. Although you can’t control whether your kids will be best friends, you can influence their relationship — also for better or for worse.

Parental favoritism (perceived or actual), for instance, can make any existing issues much worse for siblings. “When parents treat kids differently, in ways that kids feel are unfair, that’s associated with worse sibling relationships and lower self-concept,” Laurie Kramer, Ph.D., clinical psychologist at Northeastern University told us. “It’s not just the act of treating them differently, but doing it in ways that kids feel are unjustified and unfair.”

When it comes to positive influences on the sibling relationship, pe “the most important thing, per Kramer “is teaching kids how to look at a situation not only in terms of what they want, but also from a sibling’s point of view, to appreciate that there are different perspectives that are equally valid.” A good tactic for everyone to learn.