I created my Cantrell family for the mini-series in my siggie. So, Brianna being the O/C, Erik and her other siblings and parents were background characters created to fill out her own background. I used to play her in my games, to do what I wasn't able to do in the book. I've played them since Sims2, quite frankly. Erik became the Mayor of whatever neighborhood they were living in way back then. When we got a professional singer career in Sims3, I switched to Erik as the main star, if you will. He ended up living with his sister and her new husband, so I could continue to control him as he built his career. That way I could build Brianna's family, too. It took a great deal of effort for me, to let him move out. Finally the time was ready, but he had a disastrous love-life. He fell in love too quickly, without really getting to know the woman he chose to make his life-partner. Breaking things off before they walked down the aisle, usually. He finally married and they had a baby boy right away. She used to put the newborn out on the lawn, at night, in the rain. (She did this autonomously.)
When Sims4 came around I brought Erik back to be my Founder of the Pinstar Legacy Challenge. I discovered playing on normal was just too short. Erik died and then his wife died a few hours apart. I decided after I completed the challenge (when the first heir of generation ten was born) that I wanted to play him again. On LONG. Some of you have read my updates and know how often I've had to restart.
So, it's no surprise, I'm sure, that I have chosen Erik and his bride-to-be, to be the first of my Sims to play with Infants.
I also play a loose rotation, if you can even call it that. Particularly when I was playing my ancestral save. I have my favorites, that I don't like to leave, but if one of the other families was due to have another child, I would pop on over and using MCCC get that child started, or sometimes even born, if I left things too late. It's a bit more fun for me to do it that way, rather than a strict, house one, house two, house three, start again.