Your Guide To Sibling Rivalry If you have children you may have been faced with the issues of sibling rivalry. Sibling rivalry is a concern for almost every parent with two or more children. It is defined as competition and animosity between siblings that arouses jealousy that usually starts after the birth of the second-born and can continue all throughout childhood, causing a stressful time for the parents. Hence, to get a better understanding of this and how to resolve conflicts amongst siblings below is a list of some of the causes to help parents identify those causes and help children get along better by working through those conflicts in positive ways.