Is the one-third share of the apartment that the eldest brother wrote to his mother rightfully hers, and is the wife's stance in defending her mother's right correct, or is she thereby slandering her brother?

An agreement to sell the farm and distribute its price without the father's knowledge is considered void, because disposing of someone else's property without their consent is invalid. If the father reaches the age of legal interdiction, his case should be brought before the Sharia court to appoint a guardian over his assets. The father gifting the apartment they live in to your wife's mother is invalid due to lack of possession, as the giver does not reside in what he has gifted. The son who gifted one-third of the apartment to his mother cannot revoke his gift after it has been accepted and taken possession of. Your wife must bear witness to the truth if she knows it, for concealing it and lying are grave sins. If your wife's mother owns one-third of the apartment, it is her property regardless of the apartment's value, and if it is sold, she is entitled to one-third of the price.