University Park, Pa. -- Most children in the United States grow up with sisters and brothers. Connections that usually last a lifetime, these relationships can be strained at times, especially during childhood. New research concludes that sibling ties are best understood in the context of their families, and that efforts to improve relationships should take into account not just the siblings, but the family as a whole.

This research also found that, overall, sisters feel closer to their siblings than do brothers, and that relationships between sisters and brothers become closer in later adolescence. Further, for all siblings, discord is highest when the first-born child is about age 13 and the second-born is about age 10.

As reported in the November/December 2006 issue of the journal Child Development, researchers at Pennsylvania State University interviewed mothers, fathers, and first- and second-born children in 200 white, working- and middle-class, two-parent families. During the course of the study, first-born children ranged from 10 to 19 years of age, with an average age of 12 at the start of the study and 17 at the end. Second-born children ranged from 7 to 17 years of age during the study, with an average age of 9 at the start and 15 at the end.

Among the study's key findings are:

--Changes in parent-child relationships are associated with changes in sibling relationships. Specifically, changes in mothers' warmth and acceptance of their children from middle childhood through later adolescence are associated with changes in siblings' feelings of closeness and intimacy with one another. When there are increases or decreases in conflict between fathers and their children, the children show similar changes in conflict with their siblings.

--Siblings may turn to one another for support when family circumstances are difficult. When fathers say there is less love in their marriages, their children are closer with their siblings.

"This study showed that sibling relationships change across childhood and adolescence, with many siblings reporting that they have relationships in later adolescence that are more positive and have less conflict," says Ji-Yeon Kim, the study's lead author and research associate at Pennsylvania State University. "Sibling relationships are part of the larger family system of relationships and may both affect and be affected by marital and parent-child relationships."

The article, "Longitudinal Course and Family Correlates of Sibling Relationships from Childhood Through Adolescence," is written by Kim, Susan McHale, D. Wayne Osgood and Anne Crouter, all faculty at Penn State, and publish in Vol 77, Issue 5, of the journal.