So when they child aged into a teenager I think it was the child’s hair was short and they looked like a boy and it’s a girl, so how can I change the child’s hair? You should try having control of the child like where a persons character is you should have the child put into the character box also and let them customize them/ the child
*pressing* (sorry alto correction)
You can change Sim’s hair by pressure the button that looks like a shirt and going to a curtain section. Then it will give you the option to change the Sim’s hair.
Basically their hair will change as they turning older and older. But you can change their appearance by clicking that one sim you want to change their looks, and tap the makeover button that's in blue color.