Objective: Young-onset dementia (YOD) has significant impact for the affected person, but also has far-reaching effects on the family. Additionally, biological relatives have an increased genetic risk of developing the condition themselves. This review aimed to identify the psychological and social impacts of YOD in the family, for asymptomatic relatives. Methods: A systematic review of key databases for empirical studies about the lived experience of biological relatives at risk for YOD was performed. Data was collated and interpreted via narrative synthesis. Results: The majority of the nineteen included studies were qualitative and explored the experiences of children with a parent with YOD. Five themes were developed: (1) Onset of YOD disrupts family functioning (2) Emotional impact is significant and varied (3) Uncertain future (due to uncertainty of diagnosis, care-giving responsibilities, and their own increased genetic risk) (4) Lack of visibility in health care and society (5) Coping strategies include physical/cognitive distancing, and emotion-focused coping. Conclusion: Our findings demonstrate a diagnosis of YOD significantly impacts the lives of relatives, yet their experiences and needs often go unnoticed. Practice implications: We present a practical framework of questions and strategies for care of relatives, mapped to the self-regulation model of genetic counselling.