I'm wondering because I have had this theory for a couple of seasons now that the Night King might be a Targaryan - maybe even the Mad King (sounds stupid but there seems to be a lot of family connections GoT so I wouldn't put it past them)
Doubtful, there would've been some hint already if that were the case. Also, the white walkers were there since the ancient times (they already attacked; the wall was built generations ago to stop them; everyone think that there are some ancient fairy tale; etc) and we were shown how they were created (again, some very long time ago). Mad King was alive what, a couple of decades ago? Less than 30 years I guess, looking at Jaime, for example, who already served him then.
It looks much more likely that the dragons and the white walkers are natural enemies. The dead don't like fire and even the series are called ice and fire something. Also, the dragon glass and the valyrian steel (forged in the dragon's breath) seem to be the only things that can kill the walker (granted, we don't know if dragon glass is actually connected to dragons, but you have to assume that there is a connection)
It looks much more likely that the dragons and the white walkers are natural enemies. The dead don't like fire and even the series are called ice and fire something. Also, the dragon glass and the valyrian steel (forged in the dragon's breath) seem to be the only things that can kill the walker (granted, we don't know if dragon glass is actually connected to dragons, but you have to assume that there is a connection)