I couldn’t get a good enough look. My best guess is they just kept getting new themed stickers and added them. Or they did their entire extended family? I really want to say the dad is military (I think I see a cover on one the figures) and there are three sets of 6. So a family of six? I queried on Facebook and a grandma gave me a good idea:
I think they are grandparents and it starts with them and their kids and their kids grown up with their own children….etc. That’s my theory now that I am in that grandmother kingdom.