Jon Arryn was the Lord of the Eyrie, Defender of the Vale, Warden of the East, and Hand to King Robert Baratheon before the events of A Game of Thrones. He took Robert and Eddard Stark as wards and became a father figure to both. When King Aerys II Targaryen commanded him to hand over his wards for execution, Jon rose up in rebellion. To earn the support of House Tully in the rebellion, Jon married the much younger Lysa Tully. Throughout Robert's reign, Jon was left with most of the responsibility of the Seven Kingdoms. When Stannis Baratheon had doubts about the parentage of Queen Cersei Lannister's children, he brought his suspicions to Jon, who confirmed that Cersei's children were fathered not by Robert, but by her brother Jaime. Before he could reveal this publicly, Lysa poisoned him to stop him from sending their son Robert Arryn away as a ward.