How should one deal with a brother who has entered into a customary marriage (zawaj urfi) with an older woman, refuses to rectify the marriage situation, and resides with her in the mother's house?

"Urfi marriage" refers to several types:

1. Marriage not officially documented: If it fulfills the legal pillars and conditions, then there is no harm in it. 2. Marriage without a guardian (wali) or witnesses: This is void and forbidden, considered adultery, and must be annulled with repentance. 3. Marriage with witnesses but without a guardian: This is void according to the majority of scholars and must be annulled.

If the marriage fulfills the legal conditions and pillars and only lacks documentation, then there is no harm in it. However, if it is void (without a guardian or witnesses, or with witnesses but without a guardian), then its perpetrator must be advised to annul it. If they insist on the sin, then it is permissible to ostracize them if they cannot be deterred by other means.