Families of adults with an intellectual disability (ID) face post-parent transition when they can no longer assume their son's or daughter's care. This exploratory study aims to assess the perceptions of 12 mothers (Mage = 65.1; years, SD: 11) sharing a household with an adult with an ID (Mage = 36.9; SD: 11.4)): benefits and constraints of cohabitation, residence transition planning, perceptions and emotions about the future. The results of a questionnaire completed in an interview indicate that several mothers can envision siblings becoming potential caregivers for the future and that the transition generates emotions relating to their son's or daughter's welfare. However, participants' planning of the transition is not advanced in most cases.