Need help remembering story about a young boy child on a Norse or viking style planet / environment. Very abusive upbringing. His father is the king or leader of clan. Story is about him overcoming this. growing up and finding out there is a galactic empire out there. He becomes part of it. inside of himself is also untapped major power. he starts accumulating items and crew members. He changes from a boy to girl along the way. It was a female author. Multiple books in the series.