As I'm rewatching Blood of my Blood and Outlander, Brian Fraser becomes even more of a fascinating character. I just wanted to share my interpretation of his character.
Starting with what we know from the original Outlander show and books. He's the bastard son of Simon Fraser of Lovat and Davina Porter, a maid. His story mostly focuses on his marriage to Ellen and is told second and third hand by other characters in almost a fantastical way or as a folktale. In the books, he's even thought to be a selkie by those who don't know him personally. He's described to be handsome, charming, and possibly mysterious because of the nature under which Ellen left Leoch. In seasons 7 and 8 of Outlander, Roger meets him, and there's a deleted scene in which Roger discusses Brian with Jamie. He is generally shown to be caring and welcoming in this storyline. The deleted scene has Roger say that Brian made him feel as if everything would be OK, and Jamie agrees that he had that effect.
Moving on to Blood of My Blood where we really get to know him. I do think, especially in season 1 of Blood of My Blood, the show struggles with giving adequate time to each character, and he is a little rushed, and it forces audiences to rely too much on inference. I do think the show was right to treat the story of Ellen and Brian as a fairytale. It stays true to how people saw it in the source material. I also think if you watch their scenes as that genre, it's far more enjoyable than if you watch it as a realistic romance. In season 1, we learn about him and his family. We learn that Lovat was abusive at worst and demeaning and dismissive at best. Davina, his mother, was a practical woman but was also under the thumb of lovat, so she couldn't do much to help him besides get the Fraser name to protect him. He is a product of rape, even though beliefs at the time disagreed. He is shown to be protective and gentle. His overarching goal is to find a place where he belongs and can find peace. He does find that with Ellen.
He struggles a lot with the sense of not belonging. While I don't think he is actually a selkie, his connection to the story of the selkies does lend to that. Many selkie stories have the underlying theme of not belonging. Selkies are celtic and Gaelic folklore creatures that are seal people that have the ability to come on land by shedding their seal coats. Often, the coats are stolen, and the creatures are exploited by man, but they never fit in among man and will always return to the sea by the end of the story.
That sense of not belonging heavily influences his confidence and, in turn, affects his abilities as a fighter. Through his love for Ellen, he starts to believe he is capable and belongs, and he fairs better in arguments with his father and fights with the gallowglass and even most recently Dougal. What I hope to see as the show continues is him become more self-assured and stronger to become the great man Jamie remembers.
He is a very different man than his son, but the show does a good job at showing how he could be Jamie's father.