Does playing cards in Ramadan count as gambling, necessitating an expiation (kaffarah) if the loser is the one who pays, especially if the intention was to share in the payment? And is it obligatory to repay my cousin who paid on my behalf?

If playing cards leads to neglecting an obligatory duty or a right, or if it involves a stake, then it is forbidden. If it does not lead to that and does not involve a stake, then it is permissible, though disliked. Friends should be advised and the religious ruling explained to them. It is not permissible to offer money as a stake. A Muslim should occupy their time with the worship of Allah and choose their companions wisely, as the Prophet, peace and blessings be upon him, said: "Do not accompany anyone but a believer, and let no one eat your food except one who is pious."