Is it permissible to drop the claim for the amount of money paid by the father from his joint funds with his uncle to a relative of theirs without the uncle's consent? And what is the nature of the partnership between the father and his uncle, and between the father and his uncle with the relative?

The partnership between partners ends with the death of one of them. If there is common property between the father and the uncle, this is considered a co-ownership partnership (shirkat milk). However, if they collaborated in both capital and labor, it is a Mudarabah (definition) partnership (shirkat inan). Upon the father's death, the heirs have the option to renew the partnership with the uncle or consider it terminated. The money that the father took from the partnership with the uncle and invested with his relative must have its amount and profit determined. The uncle is entitled to half of it, or whatever they had agreed upon, because it belongs to the first partnership. The adult heirs may waive their share of this money to the relative, while the decision regarding the uncle's share rests with him.