I turned 31 shortly after winging, my wife had baby #3 during pilot training, and I got rolled back for medical reasons. All that said, I graduated top of the class and was selected for 1 of 2 fighters that dropped for my class of 13 students in T-38s.
Having a family provided balance and forced me to make good use of my time in the squadron so I had time for them when I went home. It’s all what you make of it. We only had one older guy really have any serious problems adapting that I’m aware of, and although we were friends, he honestly shouldn’t have been selected for UPT to begin with. At the time reservists weren’t required to go through IFS and his first exposure kicked him in the balls.
I can see where some life situations would make adapting more difficult, but in my case I never saw being older and having kids as a detriment.