The 2005 version of Le Roman de Renart is an adaptation for kids. It added magic (Pierre. WTF is this guy) and threw away the adult elements (Renart and Hersent DO fuck together, contrary to the movie in which Hersent lustfully runs after Renart who doesn't want)... In short, it's not that faithful. And the original story counts a lot of characters, and they haven't all been faithfully adaptated. Some have been replaced (there's a rat called Pelé. In the movie, it's Rufus. Renart and Hermeline have 3 sons, in the movie they have a son called Théo and a daughter called Nicolette. And so on), changed some character's roles and personalities (Examples : Renart is an asshole in the original tales. He even rapes Hersent ! Also Tibert the cat is very smart and cunning and EVEN fooled Renart once yet in the movie he's dumb. And Bernard the donkey is a very minor character and is not either a chancellor or evil), and they also threw away a lot of characters. The movie doesn't feature Chanteclerc's father Chanteclin, Tiécelin the raven, Grimbert the badger (Renart's cousin, friend and lawyer), Ysengrin and Hersent's 4 children, etc... And Ysengrin's brother, Primaut.
Here is my version of Primaut if he appeared in the movie.
My version of Primaut is a knight (because in the original stories, he's a "damp", an old French word for "lord"), who takes his duty very seriously and is very faithful to his king Noble. He's a badass who fights very good, he's very strong, smart and ready to die in battle for the kingdom, and he got many scars with time. He is 6-years-older than Ysengrin and always took care of him when he was a kid and a teen, and was very close to him for years, Ysengrin admired him a lot ; Primaut is not always there because he's always on missions as he is a knight, so whenever Ysengrn heard about the fact his brother would come over, he made anything to impress him, and that's why he wanted to become Captain of the Royal Guards, in my headcanon. So he felt closer to him. Everything lasted until the end of the movie, when everyone found out Ysengrin plotted against King Noble and Renart alongside Chancellor Bernard. Primaut lost all his trust in his younger brother. He still loves him, of course, but he never forgave him for his greed and lack of morals, and didn't wish to talk to him anymore. I don't know if we can say "heartbroken" when it's not about romantic love but fraternal love, but that's what they felt for each other whatever it's called. Especially Ysengrin, who lost the trust of his lifelong idol.

Le Roman de Renart and Ysengrin © Thierry Schiel
Primaut, drawing, 9-year-old Ysengrin's design, idea and theories © me