This exploratory cross-sectional study aimed to examine the family quality of life (FQoL) among 51 Brazilian families who have children with Rubinstein-Taybi syndrome, a rare genetic disorder. Data were collected using sociodemographic and clinical data forms, as well as the Beach Center FQoL Scale, a 5-point Likert scale ranging from "very dissatisfied" (1) to "very satisfied" (5). The average score of the overall FQoL was 3.93 ± 0.64. Families' scores were higher for family interaction (4.17 ± 0.76), parenting (4.13 ± 0.61), and disability-related support (4.08 ± 0.76) domains, and lower for the family's emotional well-being (3.31 ± 0.96) and physical/material well-being (3.76 ± 0.82) domains. Family income, attendance at religious services, presence of ocular abnormalities, and aggressive behavior explained 46.2% of the variance in the overall FQoL. In summary, FQoL seems to be anchored in aspects such as family interaction and the care of parents, and be negatively affected by emotional issues, physical, and material limitations. In this context, psychological assistance should be provided to both parents and siblings whenever indicated, for improving emotional well-being and increasing family resilience. Additionally, investments in social policies, services, and human and material resources are needed to improve the physical and material conditions of families, promote better health care, and therefore reduce the family burden.