Does the grandfather's right to one-sixth of the inheritance fall away after his death and his bequest that the building be owned by his deceased son's children, and how can this bequest be carried out, and is a written paper sufficient to prove this legally and lawfully?

If the deceased's heirs are limited to those mentioned, then the heirs are the wife and the direct children. The wife receives one-eighth, and the remainder goes to the children, with the male receiving the share of two females. The grandchildren (children of the son) receive nothing due to the presence of direct children.

The original estate: 248 shares. The wife receives 31 shares. Each male child receives 14 shares, and each female child receives 7 shares.

The written will is valid if it is legally proven to be in the testator's handwriting or if it was witnessed. It must be executed if proven by just evidence, even if the heirs do not agree.

It is not permissible for the grandfather to register the property of his deceased son in his own name without his minor grandchildren, as he is only entitled to one-sixth of the inheritance. He must act in the best interest of the orphan, based on the Almighty's saying: "And do not approach the orphan's property except in a way that is best until he reaches maturity" (Al-Isra: 34), and the Prophet's (PBUH) saying: "O Allah, I warn against violating the rights of the two vulnerable ones: the orphan and the woman."

It is advisable to refer to the Sharia court to resolve these matters.