How should one deal with the money of a maternal uncle who has suffered a stroke, knowing that some of his money was acquired through usury and some from lawful sources, and is his brother entitled to withdraw and invest his money?

It is not permissible to dispose of your uncle's money except for his sustenance and medical treatment, or if he regains consciousness and the disposal is through a financial exchange, or by giving charity/making a will that does not exceed one-third of his wealth. Distinguishing lawful money from unlawful money is difficult and requires experts. It is better to leave the money until its status is clarified. If he recovers, he himself should undertake its liquidation and determine what portion was from usury to dispose of it for the general welfare of Muslims. If he dies, the Sharia (definition) courts will rule on it. Your brother should not dispose of the money except for settling a debt or recovering lost property with documentation, and he must inform the Sharia court to oversee his money or appoint a guardian.