How you can be a half Dragon?

Sorry. Dragons are members of subphylum that branched off of other vertebrates around the time of the lob-finned fishes. Cross-breeding is out of the question. The above is only partially true. Dragons have been known to take human shape (had they the ability to shape-change at all) and mate with humans, so human-dragon cross breeds are possible, but they are just rare. Third View: Although dragons did shapeshift into humans and may have tried to mate with them, scientifically speaking, it would be very unlikely the DNA of both parents would successfully intertwine and match up to make a half-dragon/half-human child, but it's not an impossibity.