I don't think Disney had to make a connection to the Skywalkers at all. Star Wars is one of the few brands out there that sells itself.
But it makes sense that Darth Vader would have some kind of connection to this story, since he's actively chasing down the recipient of the plans transmitted by Rogue One at the beginning of ANH.
Plus he's the one that told Tarkin's little council of evil meeting that the Rebels who stole the plans had been dealt with, which means he would have to be around enough to know that.