I've seen a very good theory that when you consider that: 1, Elena and Damon both come from Traveller bloodlines (Damon via Silas and Elena via Katherine's father), 2, they're two Cured vampires with Damon literally having the Cure still flowing in his veins and 3, they're from the doppelganger lines (Silas and Amara), it's almost impossible for their children to just be normal, non-magical, ordinary humans.
Now how that magic manifests itself depends on the plot.