I see this has been out since 2020. I started playing the Get Famous pack since about 2021/22 (I don't exactly remember when I bought it). At first, my famous Sim's children would age up to children and become Rising Stars, but eventually they stopped aging up with fame period. At random times, when the 'child' is now ready to become an adult, they'll gain fame. Although, this is extremely rare and has happened a handful of times for me. They all age up with no fame at all. I'm not sure when it started, and it happens without mods in the game. I also don't even have that many mods to manage. It has been happening to me for about a year (about the time Growing Together came out I think). At that point, I owned all of the packs. Fame also seems to be hard to gain and lost even more quickly. I've had a Sim donate multiple gold toilets and the fame bar stayed about the same. It definitely wasn't like this when I bought the pack.
Use one of your Fame Points to get the Fan Favorite celebrity perk. With that perk, you can get other Sims to boost the fame of anyone in your household. Start boosting the fame of your kids and they should become celebrities pretty quickly.
