[Bruce Campbells Chin]

Except Jon made it very clear that he doesn't want to be "together" with Danaerys. As Varys said, Jon was raised as a Stark in Winterfell, and his views on incest were formed then. As Catelyn Stark said, Westeros views incest as an "abomination".

Danaerys doesn't think it's a big deal because she was raised as a Targaeryen right from birth, and so believes incest is no big deal. So while she doesn't have an issue marrying/having sex with her nephew, Jon very clearly considers that to be a deal-killer.

[morphing libertarian]

The new queen will be lonely on the iron throne