Mark Feinberg, research professor at the Edna Bennett Pierce Prevention Research Center, spoke on the Rick Sanchez podcast, where he discussed sibling relationships and what makes them different than other lifelong relationships. Feinberg’s episode can be found on Apple Podcasts.  

Feinberg argued that the bond between siblings is one of the most influential relationships across the lifespan and may be even as impactful as the child-parent connection. He said that as individuals age, one of the strongest predictors of happiness and mental well-being is the quality of their relationship with their sibling. Since siblings often share the same family environment, they play a major role in social and emotional development. 

While people will experience a wide variety of relationships in their lifetime, ranging from romantic to platonic, often the longest relationships remain those amongst siblings. Since siblings often share the same family environment, they play a major role in social and emotional development. 

Feinberg said that in many cases, siblings spend more time together than anyone else, and in the United States, children are more likely to grow up with a sibling than a father. 

Feinberg’s research has shown that sibling relationships may influence anxiety, depression, substance use and academic performance, friendships and even future romantic relationships. Sibling relationships can also have intense conflict, displaying more aggression and physical violence towards each other than any other family relationship. Small verbal comments and criticisms have the power to trigger cycles of conflict that can last for years.  

On a positive note, Feinberg shares that siblings teach each other how to manage conflict, jealousy, compromise and cooperation, through everyday interactions. They learn to balance competition with continuous support and how to function as a team unit since they share similar perspectives on their parents, family dynamics and their community. 

 “The thing about sibling relationships that’s unlike anything else in our life is we don’t choose it, it’s given to us and we deal with it for the rest of our life,” Feinberg said.  

 According to Feinberg, biological siblings may share personality traits because of shared genetics and environmental factors, but cousins or close family friends can take on sibling-like roles, depending on cultural views on family.  

 When researchers study sibling relationships, there are often questions regarding the influence of birth order, but Feinberg said that it only has a small influence on development and personality. Older siblings may experience more pressure because parents are learning as they go, making them the “rough draft.” 

 As siblings age, their relationships may shift towards discussions about how to care for their parents and reflections on shared childhood experiences. Feinberg emphasized that, throughout all of life’s stages, siblings share a unique relationship, one that’s everlasting.  

 “You never leave your sibling mentally, even if you leave physically.” 

 Feinberg has published a variety of work regarding sibling relationships. His work was featured in Siblings are special: A practical guide for adapting a universal primary prevention program for sibling relationships, which highlighted the significance of sibling relationships on development and mental health in childhood and adolescence. His work spans from foundational science on co-parenting and sibling relationships to community-level systems for scaling evidence-based prevention.