The Dragonborn Comes (To Remnant)

Y/N Branwen, the eldest child of Tai and Raven, disappeared mysteriously when he was fifteen. Despite all the efforts and favors called in, no trace of him ever emerged, and eventually the grieving family had to accept that he was gone and move on in spite of the hole in their hearts. Raven returned to her tribe, and Tai did his best to raise Y/N's sisters.

But ten years later, a strange man appears during one of team RWBY's assignments, clad in great armor and wielding immense power, and he seems oddly familiar to the sisters.