Is it permissible to favor the third wife by giving her a house registered in her name, without the other wives, knowing that the father does not treat them equally, and how can he be advised in this situation?

Justice between wives is obligatory and includes maintenance, housing, and division of time. It is not permissible for the husband to oppress any of them in these matters. As for gifts and donations, equality between them in this regard is desirable, not obligatory, according to the preponderant opinion. Justice is generally desirable to avoid animosity between wives.