Responses
The way that I know this but I also forgot the title
Oh wait i think i found it fam
https://www.mangago.me/read-manga/making_a_child_with_a_beast/
I remember the main character found this beast when they were young and took care of it and the beast marked the man and that caused other men to hate him. But the beast came back and they had a kid and went to the beasts mountain where the brother of the beast tried to fool the MC to marry him. Oh the MC was a vet as well.