What is the ruling on dividing marriage expenses between a brother and his cousin, based on the latter's request, which he interpreted as assistance?

The dowry (Mahr) is obligatory in the marriage contract, and it is sunnah to specify it in the contract. If it is not specified, the marriage is valid, and the wife is entitled to a dowry equivalent to that of women of her status (Mahr al-Mithl). The dowry must be known; if they agree upon an unknown dowry, it is invalid, and the wife is entitled to Mahr al-Mithl. What is mentioned in the question—the refusal to specify the dowry and the request to collect the expenses of the son's and nephew's marriages and then divide them—renders the dowry unknown. This necessitates Mahr al-Mithl for the wife if the contract is concluded. If it is not concluded, then a known dowry should be specified.