|Abstract||This study examined the frequency and comfort by which siblings discuss religion, as well as the presence of surface acting in those religious conversations, as predictors of relational uncertainty in (dis)confirming sibling relationships. Participants included 218 young adults who completed an online survey assessing religious conversations with their siblings, as well as the general relational context of their sibling relationship. Data was analyzed using correlations and Hayes’ PROCESS for SPSS. The results indicated that both frequency and comfort of religious conversations were inversely associated with RU. Whereas surface acting emerged as a moderator of the association between frequency and RU, frequency moderated the association between confirmation and RU. Among the more important implications of this research is highlighting that how family members talk about sensitive topics like religion is just as – if not more –important than the mere content of those conversations.