12. An estate-holder permitted by the personal law applicable to him to adopt a son, or to give authority to his widow to adopt a son for him, shall be competent to adopt a son of to grant such authority. But no adoption made by an estate-holder or by his widow and no authority given after the date of the commencement of this Act shall be deemed to be valid unless in addition to the requirements (if any) imposed by the personal law of the estateholder the fact of such adoption has been declared, or such authority has been given, by a registered instrument attested by two or more witnesses.
Where under the personal law applicable to an estate holder his widow is competent to adopt a son without receiving authority from her husband for making such adoption, nothing herein contained shall be deemed to invalidate an adoption made by her merely by reason of no such authority being so given.