[sphinx]

P.S. People have worked out the family trees in great detail, but I'm not going to look it up now. Dany going mad is to be expected. But Jon is also half Targaryen. He's a Stark on the maternal side, just as Dany is a Martell. I don't remember about predecessor generations. There are many good Targaryen's in Game of Thrones lore (just in the show, we have met Maester Aemon and Bran's predecessor as the Three Eyed Raven), but madness does run in the family.

The show hasn't signaled that Jon is unstable, but if I were writing it, I'd throw an ominous sign or two into the mix in the last episode. I wouldn't have Jon commit any grave crimes, but I'd do just enough to give people an unsettling feeling as the show wrapped up.

[ConjunctionJunction]

Danny isn’t a Martell, because her father Aerys married his full sister, Rhaella Targaryen.

[ConjunctionJunction]

Jon’s father, Prince Rhaegar, first married Princess Elia Martell. So Jon’s half-brother and half-sister were half Martell.