Sometimes I start with a single sim, but move in a starter girlfriend/boyfriend into the house next door at the same time. Or I'll make a couple with one teenager, then move them into a house and get jobs for the parents. After that I pretty much just ignore the parents and concentrate on the teen. I usually get 5 or 6 generations into a family before I get tired of them, or something happens to the save.
When I upgraded to Windows 10, I ended up reformatting my PC and reinstalling all my programs again anyway. But when I got to the Sims, I only installed the base game, one EP (Ambitions), one SP (Fast Lane) and almost all of my store stuff. I started with a single sim living in Moonlight Hollow, got married, had children, etc. I usually pick one or two traits, but let the rest roll randomly. Unless I get Insane, or a couple of other ones I just can't stand. Once per generation, I add in a new EP and/or SP, and every couple of generations I move them to another town. If you pack up all the gravestones, the base family tree stays intact, but any cousins, nieces, nephews, etc in the old town get left behind.
A while ago, I used a laptop I have that can barely play Sims 3, and installed just the base game. Then I would use that to load up store worlds, and a specific set of store content, to "improve" the store worlds. Add in venues, build themed houses, etc. Then I saved those into another folder, and use them as a starting point in a new game. I also move my simself into a house somewhere in the world. I've got a lot of stock characters I use too, based on TV show or comic book characters. Josie and the Pussycats, The Addams Family, Archie, Betty & Veronica, Johnny Test Family, Kim Possible Family, etc.
