Spend less money, save more money, then retire. I'm retired at 42 and I hardly had a top shelf career, middle of the pack at best. Even if you're starting at zero you can do it in 10 years very easily, 5 if you haven't spent every dime up till now and you are aggressive.
Do you have kids?
The answer to this question seems obvious. There are no 42 year olds that retire by merely "saving and not over spending" when even one child is involved.
Yes there are. My brother in law sold his startup and is sufficiently retired while raising my nephews. Not a common case, by any stretch of the imagination, but it's not zero.
I used my words carefully when I said "retire by merely 'saving and not over spending'".
Your brother in law did not merely save and not over spend, he built a business and sold it for a large payout.