Brenwyr was born of a match arranged by Adiraina and Kinzi. She is Kinzi's granddaughter, and her quarter Knorth blood is where her berserker trait comes from.
When Brenwyr was 6, she borrowed her brother's clothes and dressed up in them. Her mother caught her, and was angry. Brenwyr, angry in return, said, "I hope you break your neck," and her mother did.
After her mother's death, Adiraina took Brenwyr under her wing, raising and training her, teaching her to be strong and control her Shanir powers.
In her youth in the Women's Halls of Gothregor, Brenwyr became sister-kin with a Knorth girl, Aerulan. Aerulan always told her that her mother's death hadn't been Brenwyr's fault, and this gave Brenwyr strength to control her Shanir powers.
Brenwyr and her brother Brant are very close, and she names him—along with her mother, Adiraina, and Aerulan—as the only four people she has ever loved. Brant once planed to pay the ridiculously high price Ganth asked for Aerulan's contract in perpetuity for Brenwyr's sake. That same year, however, was the Knorth Massacre, and Aerulan was killed.
As an adult, Brenwyr became the Brandan matriarch. She has 4 sons, one of whom is likely Boden, Brant's nephew and heir. Given that Brant spends much of the year in the south with their Kendar, she often manages the Brandan keep for him.
↑Seeker's Mask, "Part I", I — "Lady Brenwyr of Brandan had returned to Gothregor."
↑Seeker's Mask, "Part I", I — "The Iron Matriarch, they called her behind her back for her rigid discipline."
↑Bound in Blood, "Chapter IX: Scrying Glass", II — " 'Bren, love, he's come to accept Aerulan's price.' "
↑ 4.04.1Seeker's Mask, "Part VI: Mount Alban", V — "Since childhood she had known that she was a berserker and maledight, and had prided herself on having learned to control those traits. Only that cold pride, duty to her house, and Aerulan had allowed her to live with who she was and what as a child she had done. After Aerulan's death, her life had been achingly bleak but (thanks to Adiraina's training and her brother's compliance) still largely under her control."
↑Seeker's Mask, "Part I", V — " 'You flared, my dear. A perfect example of a mature, berserker episode, the sort that always gives you such terrible headaches afterward. That's your touch of Knorth blood again, I'm afraid, the quarter that dear Kinzi gave you.' "
↑Seeker's Mask, "Part I", V — "Adiraina winced, remembering Karidia's taunt: '…manipulating bloodlines, creating monsters…' True, she had suggested the blood-cross which had produced Brenwyr, but really…!"
↑Seeker's Mask, "Part VI: Mount Alban", V — " 'When I was six. […] I borrowed my brother's clothes and dressed up in them. Mother caught me. She was furious, called me perverted, tore them off… I-I was so angry. 'I hope you break your neck.' I said that. And she did, going down the stairs with her arms full of shirts, and pants, and boots… Oh, Mother, don't! I take it back, I take it back…' She was kneeling on the floor, looking into her mother's terrified eyes, hearing the breath escape her paralyzed lungs and not return."
↑Blood and Ivory: A Tapestry, "Lost Knots" — "Speaking of berserker tendencies, yes, you should send your granddaughter-kin Brenwyr to me. You have done wonders with her since her mother's death,"
↑Seeker's Mask, "Part VI: Mount Alban", V — "Hadn't she killed two of the only four people she had ever loved? Rather than curse Adiraina or her brother that way, she would use the white-hilted suicide knife"
↑Seeker's Mask, "Part I", V — " 'Ancestors know, I loved Aerulan—but she's been ashes on the wind for thirty-four years! I was barely more than a child then. Since, I've honored a dozen contracts, borne four sons, managed my lord brother's keep, and become a matriarch on the council.' "