What is the ruling on a father allowing his engaged son to become associated with a woman who is still married to another man, and how should a father be advised who justifies his relationship with a married woman as "fatherhood," given the suspicions surrounding this relationship, considering he is over eighty years old?

It is forbidden to propose, in any way, to a married woman, because it involves corrupting the woman against her husband. The Shari'ah has been very strict regarding this, and some scholars have even gone so far as to permanently prohibit marriage to a woman who was married during her 'iddah (waiting period). One must also beware of corrupting a woman against her husband, as the Prophet, peace and blessings be upon him, said: "He is not of us who incites a woman against her husband."

Therefore, what is required is to strive for reconciliation between the spouses, for Allah Almighty says: "And if a woman fears from her husband desertion or evasion, there is no sin upon them if they make terms of settlement between them, and settlement is best." It is not permissible to accuse a Muslim of such serious matters merely based on messages, and Allah has forbidden ill-suspicion. If this were proven, then advising him gently and kindly is legally required.