Is it permissible for a relative who owns a house jointly with his brother, and also has a sister, to appraise his brother's and sister's shares of the inheritance and give it to them during his lifetime, so that they agree to waive their share of half the house, or to sell it to him?

If a man wishes for his brothers to waive their share of an inheritance from him, or to purchase these shares from them, this action is only valid after the death of the inheritor (the deceased). However, during his lifetime, all such actions are null and void because the presumed heir does not own anything at the time of the waiver, and the future outcome is unknown.