Is it permissible for the questioner to take all the wealth of his uncle, who has no children and bequeathed it to him, while the uncle has brothers and sisters?

A will (wasiyyah) is a donation of property suspended until the death of the donor, and it is permissible within the limits of one-third. The jurists have agreed that it is not permissible to bequeath more than one-third, based on the saying of the Prophet, peace and blessings be upon him, to Sa'd ibn Abi Waqqas: "One-third, and one-third is much." If your uncle bequeathed all his wealth to you, you would receive one-third, and the remainder would depend on the heirs' approval; if they approve, it is yours; otherwise, it becomes their inheritance.