Unless such adoption shall have been recognized by the Department of the Interior prior to the effective date of this section or in the distribution of the estate of an Indian who has died prior to that date: Provided, That an adoption by Indian custom made prior to the effective date of this section may be made valid by recordation with the superintendent if both the adopted child and the adoptive parent are still living, if the adoptive parent requests that the adoption be recorded, and if the adopted child is an adult and makes such a request or the superintendent on behalf of a minor child approves of the recordation.