If you look at his father and brothers this past week:
One of them gave up on trying to grow hair, and just shaved all his hair off. Not sure which one that was, I think maybe Tito? You could see the outline of what was left of his hairline, he was definitely going bald.
Jermaine appears to wear a toupee. and so did one of the other brothers.
Marlon is balding.
Joseph is bald, he appeared on one day without his hat, but generally wears a hat to cover it.
How many 50 year old men do you know who have all their hair?
Not to mention having part of his hair burned off in a freak accident.
It has been apparent to anyone who has been paying attention that Michael Jackson wore wigs in the last years of his life.
It's called male pattern baldness, it's hereditary, and several of them have it. It happens to the best of us. He was 50!