It's already been said, but MCCC for sure! I've seen some hilarious stuff happen with that mod installed. Caleb Vatore is a funny one to keep an eye on- dude practically family hops lmao. I haven't even messed with the settings if I'm honest- only thing I recommend is that if you have households you're eventually going to integrate into a story, MARK THEM PLAYED. MCCC won't mess with "played" households- I found this out the hard way. I had set up about eight different households, and when I finally got started bringing them all together, it was only to find out three of the households had completely moved apart and married three different times. One of the sims my other sim was supposed to marry had like four kids.
It was triply weird and funny because they were all Kingdom Hearts sims, so if you know the game, imagine Axel from Kingdom Hearts with like... kids from three different marriages lmao.