Okay, quick, name the story about the boy whose parents die and he has to go live with evil relatives, until a magical person sends him on a quest.
Harry Potter, right?
Or is it James and the Giant Peach?
Or make it a girl and it's Cinderella.
Or it's one of a hundred other stories which start the same exact way.
I have people tell me all the time, I'm writing a story, but I just realized it's kind of like XYZ. The truth is, it doesn't matter. Unless your story is a complete rip off, like it's about a boy who discovers a giant peach and floats off with a bunch of huge insects, it doesn't matter if it sounds a little like another story. Because the bottom line is even if I gave three authors the same basic concept, they would all come out with something very different.
So worry less about your story sounds to much like something else, (or that someone will steal your totally cool concept) and write the darn thing!