The Skywalker Gene was a genetic marker that existed in all descendants of Anakin Skywalker. Scientists did not particularly understand how it worked, or why no matter what, every single descendent possessed the gene. Anyone with the Skywalker gene possessed immense Force potential. They had a higher midichlorian count than any other Force User in the galaxy. Although originally there was only one family who possessed the Skywalker gene, over the centuries, the Skywalker bloodline had spread across the galaxy to the point where no one was quite sure how many existed anymore.