Owain is the son of Lissa, making him a descendant of the Hero-King Marth, the nephew to Chrom and Emmeryn, and the cousin to Lucina. Descending from a long lineage of legends, Owain is fond of such tales of heroism and has an imaginative mind towards theatrics and flair. Growing up, Owain became aware of one of his mother's biggest insecurities; her Brand of the Exalt never surfaced. When Owain's finally surfaced on his arm, Lissa was overjoyed to the point of tears.

By time Owain had reached adolescence and could fight, the Fell Dragon Grima was besieging the world. During one battle, his father died protecting him from an ambushing Risen Archer. In a later battle, Owain watched as a Risen killed Lissa while she was healing the wounded. Unable to save her, Owain was able to recover Lissa's wedding ring, which he wears in her memory. In an Event Tile, he also took a piece of the staff she was using, naming is "Lissa."

To keep his spirits high, he would continue to fight in his parent's memory and engrossed himself with theatrical flair in battle. While testing himself and motivating himself to grow stronger. He has ash-blond hair and gray eyes. Described as a "colorful" character by Lucina, Owain has a habit of speaking in an overly theatrical fashion that most find tiresome, and some find endearing. His over-the-top theatrics suggest a need to stand out. Always eager to engage others in duels, Owain attributes this to his sword hand craving battle, even though this is, in actuality, due to his desire to prove his mettle and improve his combat skills. Moreover, when facing people with actual bloodlust, such as Navarre, Owain quickly drops the act and desperately tries to diffuse the situation upon realizing that he went too far with it.

He gives his weapons and equipment names out of a belief that these give them more power, and is not shy from shouting impressive-sounding attack names in the heat of battle as a means of pumping himself up.