Co-residence with a married child is considered the major form of elderly care in Thailand but marked socio-demographic changes have raised concerns over the sustainability of traditional extended families. In this article the author examines the relationships between co-residence with elderly parents and children's marriages in Bangkok. Quantitative data suggest the continuing dominance of elderly parents co-residing with an adult child. In-depth interview data reveal that most children move out of the parental home at marriage, and even if they do not, conflicts can prevent long-term co-residence. Never-married children are structurally more suitable for co-residence as they typically remain in the parental home, do not have a spouse who might not get along with parents, and can more easily care for parents without the competing needs of their own families.