A moment many Game of Thrones fans have been waiting for is finally happening: Daenerys Targaryen and Jon Snow are meeting! However, despite their willingness to become allies, the history between their families ensures that it's much easier said than done. There's a lot of talk about Daenerys's father, the "Mad King" Aerys II, as they attempt to team up. Daenerys questions Varys's loyalty by pointing out that he supported Robert Baratheon's coup despite serving Aerys, and Sansa protests Jon's plan to head to Dragonstone by reminding him that Aerys killed their grandfather. Even Cersei gets in on the action when she compares Daenerys's rule to that of the Mad King's murderous one. So what's the deal with the Mad King, and how did he leave the Iron Throne?
Like his famous nickname suggests, Aerys was an erratic ruler. He was paranoid, spiteful, and obsessed with wildfire. His eldest son, Rhaegar, wasn't exactly the most moral of men either. Ignoring his wife, Elia Martell (aka Oberyn's sister), he allegedly kidnapped Lyanna Stark, who was betrothed to Robert Baratheon. The event kicked off an uprising dubbed Robert's Rebellion.
Aerys arrested Brandon Stark for treason after he protested his sister's abduction, and his father, Rickard, intended to pay his ransom. Instead, Aerys arrested him, too, and horrifically executed both Starks. The rebellion was in full force at this point, with the houses Tully and Arryn joining Baratheon and Stark.
During the rebellion, both Rhaegar and Aerys met their ends. Robert killed Rhaegar in battle, and Jaime Lannister earned the nickname "Kingslayer" after betraying Aerys and killing him as the Lannisters sacked King's Landing. In true Mad King fashion, Aerys's final words were, "Burn them all." Robert then took the throne and ruled with Cersei Lannister as his queen until his death — or murder, but Cersei denies that, of course.
Dany and Jon also have other reasons to care about Robert's Rebellion — their births. Aerys's wife (and sister, just FYI), Rhaella, fled to Dragonstone after Rhaegar's death, where she died giving birth to Daenerys. Dany and her brother, Viserys, then grew up in exile in the Free Cities, wishing to take the throne back. And as for Jon? The story of his birth is a pretty famous one among fans who've been theorizing for years. He's not Ned Stark's bastard, as he's been told forever, but instead the son of Rhaegar and Lyanna. On her deathbed, Lyanna entrusts her brother with the secret.
So it seems there's some common ground for Dany and Jon after all. Maybe they'll end up having a bonding session when they meet?