I’m afraid there’s no easy answer to your question. The various divorces may look the same from the outside but be caused by very different reasons from inside the relationships. No one knows what a marriage is really like except the people in it. Although there are some apparently shared characteristics in the men, it may well be that the marriages in question fell apart for very different reasons.
That being said, midlife crisis is very real for some men. Somewhere in their 40s, these guys realize that they’ve lived probably over half of their life. They start to wonder if the life they are living is all there is and worry that if they don’t make some changes, they never will get to do some of the more exciting things they want to do. Some make an impulsive decision to make a radical change and divorce their wives, leave their jobs, take up with their secretaries, and move to the tropics. What they often don’t realize is that wherever they go and whatever they do, they don’t leave themselves behind. Some come to their senses and try to retrieve the life they left. Others are too prideful to take that step. Still others make a go of what they see as their second chance.
I dearly wish a vitamin or a nutritional supplement was the answer. But psychological and relational problems like this can’t usually be fixed with a powder or pill. Therapy might help but that requires the guy to be sufficiently in touch with himself and what he’s doing to himself and his family to seek it out.
If you have a close relationship with your uncle, you might encourage him to go to couples therapy with your aunt. Reassure him that therapy isn’t intended to talk him into doing something he doesn’t want to do. But it can give him and the family the assurance that he’s really done everything he can to make things better before calling it quits.
I wish you well.