Here's the big question we should finally have an answered....
Who is Anakin's father? We know that its not the emperor, and we're fairly certain that it isn't one of the main characters from the prequel trilogy (i.e. mace windu, liam neeson, darth maul, etc.) because that would have been revealed. And we also know that his father is not Vader, because Vader is Luke's father and I don't think the writers would double up on that one.
I'm thinking, after seeing rogue one and understanding that a new Han Solo spinoff is coming, that Han may be Vader's brother, and that they share a common father (Maybe Obiwan Kenobi). I always thought that Vader has some hard feelings toward Han, especially during ESB when he coated Han in the iron block and shipped him back to the bounty hunter's hideout. Never really explained why all of that was necessary.