You have queried, inter alia, that,
"If adoption is declated void by court then the relinquishment deed will be valid or not as deceased has ( widow wife and mother and 2 children in which 1 is given to younger brother in adoption)"
Primarily Section 8 of The Hindu Succession Act, 1956 which deals with general rules of succession in case of males talks about heirs and doesn’t include any distinction between a natural heir and an adopted heir.
The same goes with Section 15 which states the general rules for succession in case of female Hindus. This means that The Hindu Succession Act, 1956 does not differentiate between natural and adoptive children and thus gives equal right to both of them.
Section 12 deals with the effects of valid adoption both to the adoptive parents and the adopted child. When there is valid adoption, the child is deemed to die in the natural family, and to be reborn in the adoptive family.
The rights and liabilities of the adoptive child are severed from the birth family and the child enjoys the rights and render the liability of the adoptive family. The adopted child is deemed to be a natural son.
Under Shastric Hindu law, an adopted son was considered as good as the son begotten from the lawful wedlock by birth, ‘Putrachyavaham’, means that reflection of the Aurasa (legitimate) son.
In the landmark case of Hirabai and Anr. v Babu Manike Ingale the Hon’ble court held that the adopted child loses all his rights in the family of his birth and those rights are replaced by the rights created by the adoption in the adoptive family. The right, which the child had, to succeed to property by virtue of being the son of his natural father, in the family of his birth, is, thus, clearly to be replaced by similar rights in the -adoptive family.
In the circumstances mentioned therein the query the relinquishment deed shall be invalid.