Research has shown that family and peer relationships have an impact on the stability and quality of one's romantic relationships. According to family systems theory, family dyads are likely to impact the stability of romantic dyads within a system. Yet, little is known if and how one's sibling will impact the development and maintenance of that relationship. Therefore, the goal of this study is to understand how approval of a sibling's romantic relationship impacts the quality of that relationship. Participants ( N = 168) and their siblings ( N = 118) were recruited to participate in an online survey, which included questions regarding their current and previous romantic relationships, if applicable, their relationship with their sibling, and their approval of their sibling's previous and/or current relationship(s). Data was analyzed using moderation analyses and actor–partner interdependence models. Although regression results showed no effects of sibling approval for relationship quality for either current or past relationships, the path analyses revealed that when participants approved their siblings’ relationship, the satisfaction increased, but when the siblings approved of the participant's relationship, the satisfaction trended downward. Path analyses also showed that approval did not predict the satisfaction of either participant's or sibling's last relationship. In both models, sibling and participant approval significantly predicted each other. Last, sibling closeness was not found to moderate any of these relationships. These results show that sibling approval plays a role in romantic relationships, but the impacts vary depending on relationship context.