For giving in adoption certain rules are to be observed. Being Hindu the rules for adoption to be followed are envisaged in the Hindu Adoptions and Maintenance act.
Under this act only Hindus may adopt subject to their fulfilment of certain criteria. The first of these asserts that the adopter has the legal right to (under this Act that would mean they are a Hindu). Next, they have to have the capacity to be able to provide for the adopted child. Thirdly the child must be capable of being adopted. Lastly, compliance with all other specifications must be met to make the adoption valid.
Men can adopt if they have the consent of their wife or of all of their wives. The only way of getting around obtaining the permission of the wife or of the wives is if she or if they are unsound, if they have died, if they have completely and finally renounced the world, and if they have ceased to be a Hindu. Men who are unmarried can adopt as well as long as they are not a minor. However, if a man were to adopt a daughter, the man must be twenty one years of age or older.
Only unmarried Hindu women can legally adopt a child. A married woman can only give her consent to adoption by her husband. A married woman whose husband adopts a child is to be considered the mother. If the child is adopted and there are more than one wife living in the household, then the senior wife is classified as the legal mother of the adopted child
An adoption can only occur if there is not a child of the same sex of the adopted child still residing in the home. In particular, if a son were to be adopted then the adoptive father or mother must not have a legitimate or adopted son still living in the house.
Therefore the last clause mentioned above forbids him from taking your children (girl) in adoption.