Autism Spectrum Disorder (autism) is a neurodevelopmental condition characterised by altered social communication, repetitive behaviours and restricted interests. Emerging evidence suggests that disrupted circadian timing mechanisms may be associated with certain traits of autism, such as sleep difficulties and behavioural dysregulation. Circadian rhythms are primarily entrained by the light–dark cycle but are also shaped by social cues, including synchronisation with the circadian rhythms of family members. Despite growing interest in circadian biology and autism, little is known about how circadian synchrony functions within families that include autistic children. This scoping review synthesises findings on circadian timing in families with autistic and non-autistic children. A systematic search of four databases (PubMed, Scopus, PsycINFO, and CINAHL) yielded 2,423 results, of which 25 met inclusion criteria. An additional 17 studies were identified through handsearching. The final dataset comprised 42 studies, which were organised into a narrative synthesis and thematic analysis. Six studies focused on sleep synchrony in families with autistic children, while the remaining 36 studies examined circadian biomarkers (n = 5), activity rhythms (n = 12), and sleep synchrony (n = 19) in families with non-autistic children. Findings revealed evidence of circadian synchrony in both groups, with family members displaying aligned sleep–wake patterns and daily activity rhythms. However, studies involving autistic families were relatively limited, and the mechanisms underlying circadian synchrony remain poorly understood. While this review highlights emerging insights into circadian synchrony in families, significant gaps in the literature remain. Research in autistic families is particularly scarce, and there is a need for longitudinal and experimental studies to better understand the interplay between genetic, environmental and social factors. Further research should explore whether disrupted circadian synchrony contributes to the neurobiology of autism or its associated traits, such as sleep difficulties and behavioural dysregulation. Addressing these gaps could inform targeted interventions to improve sleep and overall well-being in autistic children and their families.