I also link them as cousins to keep extending the family beyond that household.
simsplayer818, I'm curious how you link them as cousins. Do you mean you're able to do that in a way that shows in their family tree? And, if so, how? (I have a few of my older sims that I now wish I could create family links with some of my younger ones, but have yet been able to find a cheat for this.)
GameGirl2168a I add them a couple of different ways depending on the size of the family I'm going to be playing and the ages involved. I sometimes create a big family with adult or elder parents with grown kids at adult or young adult age, then (from live mode or their relationship will be at zero) I'll split the grown up kids into different households then play each household in turn. So their kids will all be cousins as they have them. I give the kids the Incredibly Friendly reward trait so they can introduce themselves to the family members they don't live with and get a relationship boost. Sometimes I make family clubs too (with Get Together).
Another way I do it is to play a household then add a sibling for a parent as I finish their household, move them out from live mode again so they know each other and play them next. I might add kids for them before moving them out or they may have kids later. I'm doing that now actually. I just went back to one of my favourite families and added a young adult sister for the dad. Her little nephew calls her all the time lol you wouldn't think she was only added in CAS yesterday 😂.
I cheat the Beloved Trait so that the family relationships don't decline traits.equip_trait trait_Legendary and I buy them the Always Welcome reward trait so they can visit any time and be like family instead of a regular guest and make themselves at home.
If I have any trouble adding relationships and family dynamics in CAS I use cas.fulleditmode to get around that. When families have kids they do show up in the relationship panel as Cousin/Nephew/Niece/Grandchild. I can't remember about the family tree though. I'll have to look at that tomorrow to remind myself. I think they do show up when the parent is clicked on, I think the kids show on the tree then 🤔. But I'll check.
Update: I checked my family trees and for me I click on the parent to expand to show kids and their part of the family tree. It's a little annoying that it's necessary to do that. I'd prefer to see the whole family tree on one screen. But it does show the other family members from different households.
Wow. Such great info, simsplayer818. Thank you. Now my mind is bursting with familial ideas for several of my sims. 😄
