New research suggests that intense sibling rivalries could lead to later mental health problems.
A study published on Monday in the journal Pediatrics found that brother and sister bullying can cause as much mental anxiety as bullying from peers.
Researchers analyzed data from more than 3,500 telephone interviews with children up to age 17.
They found that children who were attacked or physically intimidated by a sibling were more likely to report mental health problems. Many had increased levels of depression, anger and anxiety.
Researchers say that parents should know that sibling bullying is harmful, and work to help children get along.