Is it permissible to demand the money paid to lawyers after waiving the claim for land that has not been possessed, and which the uncle had previously verbally relinquished to the son?

If your uncle gifted you a piece of land, and you did not take possession of it before his death, then it belongs to the heirs, because a gift is not binding until possession is taken. Jurists have differed regarding its ruling: The Shafi'is and Hanbalis are of the view that the heirs stand in the place of the donor, and they have the option to uphold the gift or revoke it. Whereas the Hanafis, Malikis, and some Hanbalis are of the view that it becomes void upon the death of the donor before possession is taken. You do not have the right to demand from the heirs what you paid to the lawyer, unless they willingly pay it to you.