Early-onset dementia, which is diagnosed if the person with dementia is younger than 65, differs from late-onset dementia in crucial ways. It comes in a variety of forms that have different symptoms, has a lower prevalence, is less well-known, and has fewer services available that are tailored to the needs of people diagnosed with it and their families. Furthermore, it comes in a different life stage in which the family still plays a more central role. Based on ethnographic fieldwork, consisting mainly of in-depth interviews with families dealing with early-onset dementia in the Netherlands, in this thesis I show the far-reaching consequences early-onset dementia has for the lives and relationships of families. I demonstrate that early-onset dementia not only affects relationships to the sick person, but also the relationship between the ‘healthy’ parent and children or relationships among siblings. But it goes further than that. I illustrate how the illness also changes relationships to friends, relatives, and colleagues, and, finally, I discuss how the socio-cultural context shapes how the impact of early-onset dementia on relationships is experienced. The theoretical contribution of this thesis is that it argues for a systemic approach to early-onset dementia, which helps to understand the ambiguities and ambivalences that family members encounter and which are difficult to grasp using an individualistic framework. This thesis underlines that in order to understand the complexities around early-onset dementia it is important to take the multiplicity of voices and perspectives of family members into consideration.