AimTo measure the impact of type 1 and 2 diabetes mellitus (T1D and T2D) on the QoL of a person's family members/partner and assess if there is any difference in family impact.MethodsA cross‐sectional study, recruited online through patient support groups, involved UK family members/partners of people with diabetes completing the Family Reported Outcome Measure‐16 (FROM‐16).ResultsTwo hundred and sixty‐one family members/partners (mean age = 57.9 years, SD = 13.8; females = 68.2%) of people with diabetes (mean age = 57.7, SD = 20.6; females = 38.3%; T1D n = 100; T2D n = 161) completed the FROM‐16. The overall FROM‐16 mean score was 10.47, SD = 7.8, suggesting a moderate effect on the QoL of family members of people with diabetes. A quarter (24.5%) of family members experienced a ‘very large effect’ or ‘extremely large effect’ on their QoL. The family impact of T1D (mean FROM‐16 = 12.61, SD = 7.9) was greater than that of T2D (mean = 9.15, SD = 7.5, p < 0.01), with being ‘female’ and ‘parents of children and adolescents’ rendered as significant predictors of greater impact. Family members of T2D had a lower risk of experiencing a high family impact (FROM‐16 score >16) compared with T1D (RR 0.561, 95% CI 0.371–0.849).ConclusionsCompared to T2D, family members of T1D experience a greater impact on their QoL, particularly those caring for children and adolescents. These findings have clinical and resource implications, indicating a need to assess this impact as a part of routine diabetes care to support impacted family members. The FROM‐16 could assess this impact in routine practice and further facilitate referral of family members to appropriate support services.