“18. The appellant’s argument based on estoppel and on the orders made by the court under the Indian Divorce Act with respect to the custody of the children did not appeal to us. All orders relating to the custody of the minor wards from their very nature must be considered to be temporary orders made in the existing circumstances. With the changed conditions and circumstances, including the passage of time, the Court is entitled to vary such orders if such variation is considered to be in the interest of the welfare of the wards. It is unnecessary to refer to some of the decided cases relating to estoppel based, on consent decrees. cited at the bar. Orders relating to custody of wards even when based on consent are liable to be varied by the Court if the welfare of the wards demands variation.”