Anyone liking Brint because it leads to Brienne clearly does not appreciate the sheer chad bro energy that lies in keeping Brint the way he is. He's a cool guy, is strong and compassionate, let's you fuck whomever and invites you to fuck together either with another participant or even just with him.
If he wants/gets to knock Elthara up, why should I bother? I've got an entire maxed out nursery full of my children, not even counting the kitsune kits. No need to reaffirm my virility by claiming Elthara for myself too. Homies gotta look out for each other, ya feel?