How can one deal with cousins whom the fiancée considers as brothers, and limit certain behaviors such as sleeping in the same bed and kissing, while preserving strong family ties and avoiding causing discord or embarrassment?

Among the signs of faith are responding to the Sharia and obeying the Most Gracious. Customs, traditions, and whims that do not please Allah Almighty should not be used to contradict what the Sharia has brought. A woman is advised to fear Allah and to veil herself from her non-mahram paternal cousins, and not to be alone with any of them. Kissing a paternal cousin or sleeping with him in the same room or on the same bed is a greater sin. The questioner should advise the people of this household in a good manner and explain the Sharia ruling to them. If the girl is his wife, she must obey him in what is good. If she insists on disobedience, it is better to divorce her if he has already married her, and to break off the engagement if it is merely an engagement, because there is no good in one who insists on disobedience, especially since it relates to preserving honor and chastity.