Family relationships are important for wellbeing across the lifecourse and are known to be important for people living with dementia, bringing benefits to self-esteem and identity, as well as providing support for people living at home. Recent research has explored the impact of dementia upon relationships. Much of this research is qualitative in nature and rarely included in systematic reviews, however, it has the potential to provide significant contributions to understanding the interplay between family relationships and dementia and to inform interventions. A systematic synthesis of qualitative research concerning the impact of dementia upon family relationships was undertaken, using thematic synthesis. Eleven articles were reviewed, which address the perspectives of people living with dementia and their spouse and/or adult children. The aims of this review are to illuminate what is currently known about the reciprocal influences between family relationships and dementia from the perspectives of the family (including the person with dementia); and to consider the implications of these findings for research and practice. Four super-ordinate themes were identified: ‘a shared history’, ‘negotiating the impact of dementia upon the relationship’, ‘openness and awareness’ and ‘shifting sands’. This synthesis contributes to an emerging field but also highlights gaps in current understanding of the impact of dementia upon relationships and in providing appropriate interventions. Implications for research and practice are considered.