Section 21(iv) in The Hindu Adoptions And Maintenance Act, 1956
(iv)his or her son or the son of his predeceased son or the son of a predeceased son of his predeceased son, so long as he is a minor; provided and to the extent that he is unable to obtain maintenance, in the case of a grandson from his father’s or mother’s estate, and in the case of a great grand-son, from the estate of his father or mother or father’s father or father’s mother;
