80s/90s movie about a kid with psychic powers?

Sean Saughn Asked: 80s/90s movie about a kid with psychic powers?

I don't remember much about this movie except disjointed pieces, but bear with me:
There's a little boy, who has an older sister. (For some reason the parents aren't there…or appear later, the story seems to have to do with neglecting your children.)
The boy at one point opens a book and a woman astronaut comes out, along with the largest hairball (the "bad guy" promises him more because he's apparently powerful).
At one point they travel to a land that's ruled by conformity, and people who do not obey get taken away….the sister ends up having to save the brother, who at one point almost becomes evil.
The true "bad guy" turns out to be a giant brain…or something like that.