In our (Active Senior Adult), community at least one member of the household needs to be 55 (they had to allow for the trophy wives). :B
A small percentage of the community can be under 55 and every household fills out a form denoting the ages of all residents every year (the form comes with our bi annual HOA dues.)
What is prohibited and enforced is anyone under 19 can not reside here, vacations, holiday visits excepted. These are the rules and everyone who lives here has to acknowledge them before moving in. I am not anti kid, heck I'm a former child myself (though my bride might dispute the "former").
If this is not your cup of tea there are lots of other choices out there. Works for us.
:C