While family studies experts acknowledge the lack of research on adult sibling jealousy, a 1982 study found that nearly half of adults studied felt a sense of rivalry toward a sibling. Either long-simmering resentments held over from childhood or envy about a sibling’s job or romantic life can cause rifts.

Adult sibling rivalry isn’t always rooted in poor childhood dynamics. As siblings get older, they follow their own paths as independent adults that may not go as planned. Feelings like jealousy and envy can amplify rivalry into a state that disrupts the family dynamic.