This study investigated the dilemmas faced by emerging adults serving as supporting siblings (SS) for their sibling with depression (SWD). A thematic analysis of 49 interviews revealed the family system as central to sibling depression. Family histories of dysfunction contributed to SWDs’ lasting symptoms, prompting SSs’ felt obligation to their sibling. SSs managed mental health communication in the family by protecting their SWD against their parents and withholding their own mental health challenges. Additionally, this study revealed SSs’ double binds: They were caught between their loyalties to their SWD and parents, and between maintaining their family system and their own well-being. The importance of family systems, family history, and challenges related to navigating sibling depression are discussed.