For me, it's a only a few, but very well developed characters who enjoy living in comfort and luxury and observe what happens around them.
My first sim ends as my primary one, whom I control 99% of the time. From that point, I complete aspirations, careers, explore the world and so on.AS for families, I do end up getting married, but as a user of certain mods, I'm not above pursuing companionship of other sims. AS for children, I never have my own biological ones. There are more than enough kids who need parents.
My main past time is wander around and help out families with their own kids :)
In short, a couple of power-leveled sims who achieve a lot and then spend time doing basically whatever.