You get what descendant means right? Kings race was dying out, there are not many purebloods like King left. I'm saying down the line Sora once had a lunalia ancestor but through the generations her bloodline has become more human due to breeding with humans.
However, if the medicine empowered all of Soras lineage factor within Sanji to allow him to fight off the changes, I dont see why him being able to awaken an ancestors ability doesn't fit with one pieces brand of pseudo scienc.