Generally, under 55+ rules, the 30 year old son would be allowed to live there. It’s no one under 19. We had a few couples who had much younger wives, maybe in their 40s. As long as one of the couple on the deed is over 55, it’s ok.
Not in my parents 60+ community. Residents must be over 60. I think they put that in specifically to address the Peter Pan syndrome.