While the Wall might never be rebuilt, the dust has settled since the season finale of Game of Thrones — an episode packed with scheming sisters, a zombie dragon, and a weird kind of romance known as incest. Yes, one of the big reveals on Sunday was that the King in the North, Jon Snow, and Mother of Dragons, Daenerys Targaryen, had boat sex — or as you’d say in Westeros, they performed a song of fire and ice. The bummer for the ignorant young lovers is that they’re actually aunt and nephew.

In a show where family is everything and Houses battle to take control of the throne, it’s impossible not to ask: How fucked up are Jon and Dany’s potential children going to be?

University of Aberdeen geneticist Jonathan Pettitt, Ph.D. has previously confirmed a Reddit theory that the pair share 44 to 47.5 percent of their DNA. That is very related; siblings share 50 percent of their DNA, monozygotic (identical) twins share 100 percent, and two unrelated people normally share zero.

Pettitt tells Inverse that the match isn’t genetically sound. Any kids that are produced from this familial union wouldn’t exactly be the healthiest, but he points out that in a world where Targaryens routinely marry and reproduce, it could be worse:

“Jon Snow is not so inbred as Dany, so their offspring would be less inbred. The inbreeding coefficient of any child of Jon and Daenerys would have an inbreeding coefficient (calculated as half of their relationship coefficient) of 22 percent. So, slightly less than that of Charles II of Spain, though not by very much.”

Kit Harington and Emilia Clarke aren't so keen on their union.

To say that a baby is going to turn out better than Charles II of Spain, however, is not saying very much. The real-life ruler and last member of the Spanish Hapsburgs was one gnarly-looking man. His inbreeding coefficient — a number that captures the degree to which his ancestors committed incest — was 25.4 percent (Dany’s is 37.5 percent). Charles II allegedly had a large misshapen head, was unable to chew, and was mentally disabled.

Dany’s lucky that Westeros doesn’t seem to follow the same genetic laws as the real world. She’s even more inbred than Charles, yet she’s still somehow beautiful, intelligent, and fully capable (if you ignore her occasional bad decision-making, like consanguineous hookups).

If George R. R. Martin’s magical incest rules didn’t apply, says Pettitt, any babies Dany had with Jon “okay, maybe you know something” Snow would be unfit to rule.

“They would still be predicted to be fairly sick based on real-world genetics,” says Pettitt. “So, overall, not likely to be great material for founding a future dynasty!”