Robert's Rebellion failed, it crumbled into little pieces and left Robert himself hanged for treason and TywinLannister put on a spear for ordering the assassination of the Targaryen children, with Eddard Stark saving Rhaenys and Aegon Targaryen in the process. The Lannisters are given an ultimatum: either bend the knee to the new king, King Rhaegar Targaryen or face the traitor's walk. For his bravery, Lord Eddard Stark is made King in the North while Rhaegar marries Lyanna Stark. A Targaryen always sits on the iron throne, while outside forces gather and form alliances, the House of the Dragon calls on their dragons to watch over them in their time of great need. King Rhaegar would rather see the realm burn to ashes than to ever lose the iron throne that is for sure.

ASOIAF AU centered years after the failure of Robert's rebellion, an AU where Jon Snow never existed instead he existed as part of the Targaryen line officially. Sansa Stark grew up a Princess and House Bolton grew too greedy where they plot to overthrow the Stark's. The game of thrones, you either win or you lose, there is no middle ground.