Jaina/Jacen
Maybe - there's no one to stop him though. Apparently he thinks Grandfather was right, and that he's the one to fulfill what Grandfather didn't get done.
I don't think it's common knowledge exactly, and I didn't want to tell Mom and Dad. He doesn't seem to be any of us, exactly, so it's not exactly - but I know Mom worried enough without learning those fears come true in this galaxy.
We've got to try to stop him, the two of us. I wish Anakin were still here.