Basically Rex is that type Dense, Loud, strong MC, like asta he was small and at middle of the game (i kinda forgot which part lmao) Fans doesn't think that he into Romance (its because he said he love "everyone" to one of female Lead).
The Surprising Part is, in the next Game (Xenoblade Chronicles 3) WE FANS were Wrong. He Went Gigachad and "married" all 3 female lead/heroines and have baby with them (in the scene there is group photo that had Rex on it, implying that he "married" all 3 female lead and had babies with each of them)