Escape to Witch Mountain by Alexander Key
Tony and Tia are two orphan children raised by a surrogate grandmother. Readers never get to meet that grandmother since she is killed in a car accident just before the story begins. The two orphans enter the foster care system, which is pretty much like every literary foster care system since Dickens, i.e. terrible. They are carted off to an orphanage where they come in conflict with the unsympathetic owner and the bullies. Tony reluctantly gets into a fight with head bully Truck. He has incredible fighting moves that let him beat the physically superior and armed bully, which makes the other kids happy if not the owner. He can also make inanimate objects move by will power. Tia has her own special powers. She can't talk but every door she comes to she can get through, locked or not. She has a soft spot for animals and has been in trouble for setting them free before. Also, she easily communicates telepathically with Tony, so there's clearly something different and unexplained about their origin. A chance clue leads them on an adventure in search of their family and their true origin.
I remember watching the movie version of this book along with a bunch of sequels on TV as a kid and loving it. Listening to this audio book, I realize I remember almost nothing of the plot other than the surprise origin revealed at the end of the book (which is spoiled by the cover of the book). Even knowing the ending, the book is very satisfying. The characters are interesting and plenty of action keeps things moving along. The narrator is Marc Thompson, who does a fine job portraying a variety of characters and evoking various moods in various scenes.
I recommend both the book and the audio version. I'm curious to watch the films again.