his only brother cheated him

Funnily, there is always such a person in any families. One would call this friend of your father the black sheep of the family - the one who brings disgrace to his own family. A leopard will never ever change their spots too. One mistake committed should only be given a single chance. Once that chance is over, never ever believe that he will change ever again. A person's personality becomes quite fixed in nature at a age over 30 years old. So, I doubt that he would be changing any time soon unless something major and bad happen to him, and he is mature enough to wake up and learn from his past mistakes. Sure, people might say that blood runs thicker than water. But, in the case of your father's friend, his friend can just forget about recognising this man as his brother. It may sound cruel, but your father's friend is not helping his brother at all by not being hard hearted. Let him learn through the hard way, when he no longer has any kins nor true friends by his side. Hopefully then, it would not be too late for him to wake up and learn.

Is sounds like the saying that every family has a black sheep.