The eighth son of a seventh son. He isn't supposed to have the power. The seventh son doesn't know why his power is late in coming. But Eren does. He knows why Roden cant use it. Because it was given to him instead. The eighth son. The flaw.
The day when the Seeker comes, the truth is revealed, and Eren is taken from the simple life he lived, to join the fight that lurks in the shadows of the normal world.
BTW, their birth order is Adron, Vertraen, Renon, Talon, Breen, Skolan, Roden, then lastly Eren.
A baby was left behind after a long war between Frost creatures and humans. A king took him in and took care of him with his other son, being that boy and the king's boy to be "brothers". Upon him growing him, he got into quite a lot of trouble that at one point he got banished from his homeland. He was looked down upon for being different from others. Banished from his relame he seeks for a fresh new future. He goes and seeks to another world to stay in being Midgard(Earth). Hoping for a better life.