Replying...
Intro. Ubbe is Ragnar and Aslaug's first son. It was conceived outside of marriage, which would have turned it into a bastard, but with Ragnar's marriage with Aslaug and the divorce of Lagertha became the son and legitimate heir of Ragnar. He is Ragnar's second oldest son and possibly the softest. He also looks a lot like his father when he was young. He was married to Margrethe, but he is now married to Torvi, who was previously his older brother, Bjorn's wife who now has a son with her called Ragnar in honor of Ubbe's father.

Ubbe Ragnarsson

@Cecilia Venier Baffo