It's clear that something's going on between Jon Snow and Daenerys Targaryen on Game of Thrones — something that goes beyond striking a deal for dragonglass. There have been plenty of significant glances and brushing of arms (the key signs of a burgeoning period-piece romance), plus Davos has indicated that he's aware of Jon's wandering eye. But there's one tiny obstacle preventing Jon and Dany from a potential love connection: they're related. But just how Daenerys and Jon Snow are related on Game of Thrones is something that needs a little untangling. Because when it comes to this family tree — well, it's complicated.
Jon's lineage is a tricky subject. Though Jon never knew who his mother was, he had always believed himself to be the bastard son of Ned Stark and some unnamed woman he met during the war of Robert's Rebellion. And because Ned was so good at keeping the secret about Jon's true parents, he never gave any indication that that wasn't true. However, fans were treated to the real story during one of Bran's visions in the Season 6 finale, where it was finally, at long last revealed that Jon was actually Ned's nephew, not his son. Jon is the son of Ned's sister Lyanna and crown prince Rhaegar Targaryen, both of whom died around the time of Jon's birth. It's Jon's Targaryen ancestry that leads back to Dany.
Luckily her origins are much easier to trace, and much less shrouded in mystery. Dany is the youngest child of Mad King Aerys Targaryen and his sister wife Rhaella; her two older brothers are Rhaegar and Viserys. Rhaegar was married to Elia Martell, with whom he had two children, but apparently he was also interested in Lyanna. His decision to abscond with her was what sparked the war that took the Targaryens from the throne. Lyanna was engaged to Robert Baratheon, who started an entire rebellion just to try and get her back. He — along with most of the Starks — believed that Lyanna had been kidnapped by Rhaegar, but stories vary. Some believed they were secretly in love.
After leaving town with Lyanna, Rhaegar set her up in a Dornish stronghold called the Tower of Joy. That was where Jon was born, and where Lyanna passed away right after handing her newborn off to her brother Ned. Rhaegar is Jon's father and Dany's brother, making Jon and Dany aunt and nephew. That could make a potential romance err on the side of ick, though for Targaryens that's basically nothing; after wedding sister to brother for centuries, an aunt and nephew is no big deal.
Jon and Dany don't know how they're related yet, either. Bran and the audience were the only ones to get the memo, but once the news makes the rounds, it's going to have a huge impact on how everything unfolds.