What is the ruling of Islamic law regarding the marriage of a young man to his married paternal uncle's daughter, who has a child and does not wish to live with her current husband, and desires to leave him, especially given that she never wished to marry him in the first place? And what about the custody of the child in the event of her divorce and marriage to this young man?

A person must be balanced in their emotions, because excessive and boundless love leads to the corruption of life. One should not remain attached to the love of a married woman. Rather, it is more befitting to send someone to her to advise her on how to deal well with her husband. Beware of being the cause of your cousin's divorce, for the Prophet, peace and blessings be upon him, said: "He is not one of us who incites a woman against her husband." Striving to corrupt a woman against her husband is an act of devils. Therefore, stay away from this woman. As for your question about her divorce and the custody of her child, that is a premature matter that she can ask about if it occurs.