This paper elucidates the difference between the fathers' care of children in single income families and double income families, and the relationships between the fathers' care of children and their social adaptability. Subjects consist of members of single income families and double income families. Both families are unclear ones. Children are of the pre-school age. Major results are as follows: 1) The fathers of double income families tend to participate more in the care of their sons than the fathers of single income families. The fathers of single income families tend to participate more in the care of their daughters than the fathers of double income families; 2) Home discipline by the fathers is related to their sons' social adaptability from 1 to 3 years of age in double income families, and it is related to social adaptability of the sons and daughters aged 1 to 3 in single income families; 3) The home environment that is the result of the mutual understanding of the father and mother on the policy toward their children's care is related to the social adaptability of their daughters in the 4 to 6 year -old bracket.