Okay so there's this book I read, probably back in 4th or 5th grade. Definitely dystopian sci-fi.
It was about this family of aliens with like special blue hair, and they went to this dystopian dimension. In the dimension I remember the sick or the old were killed and they all wore the same clothes, I think. The ending of the book was about the family trying to stop their grandmother from dying due to the old age thing and then escaping the city.
If you can help me find it, thank you; I wanna reread some old books I used to like. <3