Calling your kid sister a "fat slob" or your big brother "ugly and disgusting" is not just part of growing up with siblings—it's abuse, Dr. Robin says, and she urges parents not to tolerate it. "I want, when some mean harsh statement is made, for you to get right in the mix, right in the middle and say to them, 'This is unacceptable, its going to stop as long as you live in this house,'" Dr. Robin says.

If children or teenagers feel they have the power to say whatever hurtful thing they want to a sibling, Dr. Robin says that behavior will continue into adulthood. "They are going to take that horrible, mean behavior and they are going to take it to school, they are going to take it to college, they are going to take it into their adult relationships, and they are going to create a mess," she says.

Dr. Robin says the first step to dealing with this problem is to call it abuse and deal with it seriously. "When someone speaks in a way that is unkind, that is mean, there is a consequence that the whole family agrees to," Dr. Robin says. She says parents need to lead by example and show their children what honor, love and respect look like.

"Our families should not be the place where we are most wounded, where we feel really like we are a loser and not enough," Dr. Robin says. "[Give] your kids a foundation, so when the world tries to tell them that they are not enough, they will have a true, real structure internally in them that will be able to combat every lie that the world will give them."