It is commonly assumed that in developing countries, age at marriage of males is lower in joint than in nuclear families because males in the former type need not support their wives and children and entrust that responsibility to the large family system. But available evidence shows that age at marriage of males is lower in nuclear than in joint families and that wives and children far from being a liability are an asset and the need for female labour is more acute in nuclear than in joint families. There is no clear relationship between age at marriage of females and family structure.