Hello! New player, same issues. Just diving into this discourse in the shared frustration of trying to figure out why my sims holidays aren't working for everyone in the household.
I did see the October 31 post referenced here, I have another stipulation to add!
I have a household where I have 1 sim that was created, 1 that I think was taken from the in game stock (I had her marry him) they adopted 3 children. She was dead and brought back to life by another sim...some time after she revived they moved in a new house and adopted the kids, aged all them up to teens, and only the teens are the ones that get the holidays. There's also a cat.
When I first downloaded seasons I made a new family and a new house, they experienced the holidays with me for the first time. This household I made a husband and wife, a teen boy, a teen girl, and a boy child, and twin girls. The husband and wife I made first in CAS, they do get the holidays. Their teens I made second but they do not have the holiday banner. I just made them, though, I didn't use the biology option. I did use the biology option for their youngest boy, he is a child and he has the holiday banner. When I made him his slot moved to slot 3 (parents 1 and 2) even though his two elder siblings were made first. Then I made the twins, who also do not have the banner. After I went back into CAS and exited while making this post to make sure I explained my process right, the boy is now at the end of the slots (7). This did not change who has the banner in the household, though.
I hope that we get this fixed soon without me having to download things into folders I don't understand (from Reddit)...I'm too new at this to be modding yet. I just learned you can do cheat codes that aren't just "motherlode" for goodness' sake lol!!!