Is a will obligatory for the son of a deceased daughter during the grandfather's lifetime, especially since the grandfather referred to him as "this child is the third of his maternal uncles," or is he considered an heir through his mother?

The daughter's son is not an heir to his grandfather; he is considered to be among the relatives by affinity (Dhawi al-Arham). Therefore, the grandfather's bequest to him is valid and enforceable within the limit of one-third. If the grandfather bequeathed to his grandson the equivalent of the share of one of his sons (the mother's brothers), then this is a bequest equal to the share of a specific heir.

The estate is to be divided as follows: the mother receives one-sixth due to the presence of a lineal descendant (heir of a branch), and the wife receives one-eighth due to the presence of a lineal descendant. The remainder goes to the two sons and nine daughters by 'asabah (residuary heirs), with the male receiving the equivalent of the share of two females. The two full sisters are excluded (mahjub) by the son. The grandson, who is the legatee, is given a share equivalent to that of one of the sons.

The estate is divided into 346 shares: the mother receives 52 shares, the wife receives 39 shares, each son receives 34 shares, each daughter receives 17 shares, and the grandson (the legatee) receives 34 shares.