Daughter in law returned to India claiming she will not stay with son.

In case he wants his wife back, then your son will have to file an application under Section 9 of Hindu Marriage Act, according to which he can seek directions from court thereby asking his wife to stay with him.

Further, with respect to custody of your children, if  your children are minor then you need to file a petition for the custody of the children.

Section 6 of The Hindu Minority and Guardianship Act states that the ‘natural guardian of a Hindu minor, in respect of the minor’s person as well as in respect of the minor’s property, in the case of a boy or unmarried girl is the father, and after him, the mother, provided that the custody of a minor who has not completed the age of five years shall ordinarily be with the mother. For appointment of declaration of any person as guardian, the court shall consider the welfare of minor.

The welfare of the child is determined neither by the economic affluence nor a deep mental or emotional concern for the well being of the child. The answer depends on the balancing of all these factors and determining what is best for the child’s total well being.