Is the wife obligated to inform her husband that his father sexually harassed her and attempted to touch her body and kiss her, knowing that informing him of this might cause family problems?

Scholars have permitted kissing one's maharim (unmarriageable kin) on the head, hand, and forehead, and so forth, if there is no fear of lust or temptation, based on the hadith of the Prophet, peace and blessings be upon him, kissing Fatimah. Imam Ahmad permitted kissing maharim upon their return from a journey if one is secure from temptation. However, kissing the mouth is stipulated to be avoided because it is a source of temptation. What the husband's father desires—kissing the mouth, touching the body, and hiding from people—indicates his ill intention. Therefore, it is not permissible to be alone or secluded with him, and he must be threatened with exposure of his actions. The husband should not cut ties with his father but continue to honor him, advise him, and pray for his rectification.