He was not legitimate, but neither were most of his siblings, by the time he’s old enough to talk there’s about a dozen of them, spread across three mothers. His mother was pretty in her youth, but smart enough that she was kept around even after that.
His father (who he calls “The Baron” or “Sir”) is kind but not soft. All his children go to the same tutors and learn together, and has an armsman beat the worst performer each week, regardless of who their mother is.
One of the few times they ever speak alone is after he’s broken his (legitimate) younger brother’s arm, for calling his mother a whore. His father tells him that he’s very proud of him for defending his mother’s honor. And the hot marble of pride burning in his stomach lasts long after the welts from his whipping have healed.
He’s good with the sword, the bow, and the spear. As he gets older, he drills with the armsmen and commands them on occasion. He joins his father and elder brothers on hunts, and those are some of his favorite times.
He is surprised when their family priest recommends him to seminary. Years later he wonders if The Baron pushed for it, either as a favor or because of worries about the succession. He’d had the occasional guilty fantasy of his eldest brother, the legitimate heir, dying in some freak hunting accident, and him being so impressively brave he was named instead. But would never have acted on it.
Seminary was fine. His memory of the early parts is somewhat hazy, but he continues to be academically passable and martially talented, so an army assignment is both unsurprising and welcome