Does my father have a right to the land his uncles bought with the money he sent, and is what happened considered devouring an orphan's wealth?

Your father can claim back from his uncle the amount of money he received, because his uncle's expenditure of the money for the younger uncle's marriage without his permission is an encroachment that does not negate liability. "The hand is responsible for what it has taken until it returns it." A trustee is only liable for an transgression on his part. As for the land your father's uncles bought, he has no right to it, because if you entrust someone with dinars and he buys merchandise with them, you have no claim on the merchandise itself. An orphan is one who lost his father while he was a child. If your father had reached maturity, he is not an orphan, but that does not diminish the sanctity of encroaching upon his money.