I've made things very complicated for myself. :D
I went ahead and started making a few of the families, because they are related to existing sims in the game. So I needed to open up those families in CAS and add their relatives, then move the new branches of the family out. Then I decided maybe I would age some of them down and play through their earlier lives. For one family, it's relatively simple; I just wanted the parents to get their university degrees and get a good start on their careers because they are both very ambitious and materialistic, and they will definitely want to display their diplomas in the study.
But then I started to make my orphans' extended family, and it became quite complicated very quickly. I had originally wanted Agnes and Agatha Crumplebottom to adopt a young orphaned niece and nephew. However, once I realized they were special NPCs and that would be more complicated, I decided to create a new elder sim, Amelia Crumplebottom. So I opened up the Goth household, and created an elder Cornelia Goth, who I am going to let live for a while, at least until she develops relationships with the grandkids. Then she's probably going to become a ghost eventually. Then I created her sister Amelia Crumplebottom and moved her out; I probably won't do anything else with her until the pack arrives. Then I created another sibling, Rupert Crumplebottom. I moved him out into a third household. I am thinking that I am going to take him back into CAS, age him down to a YA or adult, and give him his wife Winifred and their twin daughters Primrose and Pandora, then play them until the girls grow up while we are waiting for Cottage Living. Eventually Primrose will marry Giles Kensington and they will have a daughter Daisy. Pandora will marry Felix Foster, and they will have a son Tom.
After Cottage Living arrives, I'm going to have Rupert, Winifred, Primrose, Giles, Pandora, and Felix all die in some mass casualty family tragedy. (Fire would probably be easiest, but I don't want burning or electrocution ghosts; maybe they could have a big pufferfish feast.) Then Great-Aunt Amelia will move back into the family home to help raise Daisy and Tom. Most of the dead family will also return as ghosts, although I think that will make the household too large, so one of them will have to move on peacefully. Either way, big family graveyard! I'm currently thinking I'll put them in the Moody & McMillan house, once I evict those nice old gentleman, but I'm not certain.
If I can figure out how to do the cheats, assuming there is a way, I'll probably go ahead and make Agnes the sibling of Cornelia, Amelia, and Rupert. Basically, the Goth-Crumplebottom family tree just leafed out in a big way. And I now have plenty to do to keep myself entertained for the next 12 days.