Purpose <p>This study examined the differences in physical and emotional sibling violence and attachment in close relationships in adulthood between lesbian, gay, bisexual, and heterosexual individuals.</p> Methods <p>Survey research was conducted using the sub-Reddit platform “/r/SampleSize: Where your opinions actually matter” which led to a sample of 1501 lesbian, gay, bisexual, and heterosexual individuals who responded to items on adult attachment in close relationships and physical and emotional sibling violence.</p> Results <p>Those individuals in the lesbian, gay, and bisexual group reported significantly higher frequency of physical, emotional, and total sibling violence than the heterosexual group. Similarly, those in the lesbian, gay, and bisexual group also reported more issues with comfortability with closeness and intimacy, comfortability depending and relying on others, and concerns with rejection and abandonment leading to anxiety in close relationships in adulthood than the heterosexual group. Regression analysis indicated both frequency of physical and emotional sibling violence in childhood and sexual orientation were related to attachment in adulthood.</p> Conclusions <p>This study highlights that both physical and emotional sibling violence and sexual orientation may influence adult attachment in close relationships. Despite lesbian, gay, and bisexual individuals reporting higher frequency of physical and emotional sibling violence than heterosexual respondents, both groups experienced this form of family violence thereby warranting therapeutic considerations for both groups.</p>