i need help with problems with aging

so are you stuck - or do you mean you dont wont to die ?

Well they won't age because you keep changing their lifespan! Either you stop or your cousin stops. [If you want them to age].

FIRST: Check to see if your sims life span is "short, medium, long or epic" if its long or epic, they don't age quickly ofcourse, so check that first, if you had theirs set to normal or short, they age very quickly.

Also, if you have upgraded your game, there is a new check box, so look at that too.