My oldest daughter is 21, but she's still "one of the kids".
I know she's an adult now and will be finishing college next year, and out loving her own life very soon, but she's still my child. Even though you can go do anything an adult can do, you are still the same "child" that you're family has known since you were born. It's going to take time for them to get used to that.
Legally, turning 18 instantly makes you an adult, but it's going to take a lot longer than that for other people to realize it.
Also, early twenty something's ARE still kids. Very few people that age have actually "grown up".
Stardew Valley. I'll run for mayor and finally kick that asshole out of office.