Is talking to a cousin (male) over the phone – within the bounds of propriety and without delving into emotional conversations or the past – considered marital infidelity, especially given the wife's love and appreciation for her husband and her desire to have children with him, and the cousin's continued unmarried status?

Talking to a male cousin (ibn al-khala) is impermissible and constitutes betrayal of the husband, due to the harm it would cause him if he found out. This is because it is the husband's right that his wife not speak to a non-mahram man without his permission. Indeed, the Messenger of Allah (peace be upon him) forbade "women from speaking [to men] except with the permission of their husbands."

These conversations must cease immediately, in obedience to Allah and to preserve the family and children, because if the husband becomes aware of this, it could destroy the family and erode trust. Satan will not be content with mere conversation; he will strive to lead both of you into immorality. Therefore, it is obligatory to fear Allah and repent to Him.