In the Ynglinga saga, Snorri Sturluson tells what happened a few generations after the deaths of Alrek and Eirík.
The Swedish king Aun was not a warlike king and had been chased away from his kingdom by Halfdan. When Halfdan had died, Aun returned to Uppsala to rule his old kingdom. After having sacrificed one of his sons to Odin, the god let him live for another sixty years. However, when twenty-five years had passed, a Danish prince named Áli the Bold appeared and chased Aun to exile in Götaland. Áli ruled for twenty-five years until Starkad appeared and killed him. Then Aun could return to his kingdom and ruled it for another period of twenty-five years.
Read more about this topic: Starkad