Brynden grew up in the in the shadows of The Twins after his father extorted the Tully's in exchange for their ancestral keep. His father, Randyll, always looked down on his sons as unworthy, mostly keeping them from attending feasts and tournaments and instead lavishing his attention on Brynden's cousin, Damon Lannister, hoping to ride the coattails of House Lannister to better position for the Freys. Brynden took umbrage with this slight and sought to prove himself in his father's eyes.
Brynden trained and studied for fifteen years, becoming adept at both the sword and the lance.
During Randyll's ambush on Harrenhall, Brynden was set to guard the wayn which carried his siblings and mother. Brynden begged his Lord father to be admitted to the war council and received nothing but a cold shoulder and a colder smack to the face before being sent away.
Witnessing the failed siege, Brynden took leave from the camp with his mother and three siblings. Fearing retaliation from Lord Emmon Baelish, they drove not toward the Twins but instead to the relative safety of The Rock. During this journey, Brynden lost his younger brother, Alester, to disease, and later, Tywin Frey and his mother to bandits in the foothills. Following this ambush, Brynden took his sister, Alyssa Frey, and turned to the open Riverlands, once again toward their home at the Crossing. At the age of six and ten Brynden and his sister reached the ruins of Oldstones where they met men who were sworn to the new lord Tylor Mallister. From these men they learned of their father's (and supposedly their own) deaths, as well as the passing of The Twins to their uncle, Jason Frey.
With the Riverlands still under siege, this time by the savage Ironborn, Brynden accepted the party's invite back to Seagard. Once safe within the walls of Seagard Brynden sought protection from his father's bannerman, Tylor Mallister. He met with the maester of Seagard and asked his and his sister's survival be kept secret. Whilst in hiding, Brynden studied naval tactics and trade until his eighteenth name day.
With the news of the passing of the Twins and the Lord Paramount of the Riverlands to his cripple uncle Edwin Frey, Brynden decided it time to return to claim his birthright. Ever the pragmatist he left his sister a ward of the Mallisters to remain dead until she could be used for a strategic marriage.
Returning to the Twins, Brynden was able to peacefully claim his birthright and become Lord of the Crossing.
The Spring Without Sun hit the Riverlands hard. Still new to his seat, Brynden attempted to keep his lands above water, commissioning repairs of flooded fields, fishing villages, and bridges throughout the Riverlands, as well as keeping his people safe from the bandits and reavers who had become numerous during the time of hardship.
During this time, Brynden also hosted a feast for the powerful houses of the Riverlands. Afterward, in a private council, he petitioned the likes of Cortland Darry, Myles Piper and others, to help him in convincing King Damon Lannister to replace him with his uncle, Edwin Frey, as Lord Paramount of the Riverlands.
The end of the third era saw Gylen Hightower's declaration of kingship delivered to the Twins. Upon reading the letter, Brynden called his banners and marched for King's Landing to answer Damon Lannister's summons.
Brynden treated with the King and Queen, Damon Lannister and Danae Targaryen, convincing them to honor the petition written by his bannermen to become Lord Paramount of the Riverlands. He fought the rapid rise in power of Septon Terrence Fossoway, which was resolved when the good septon died of deteriorating health.
Brynden took Riverrun from his cousin, Addam Frey, and returned it to House Tully. Thereafter, he traveled to Seagard to deal with traitorous vassal Denys Mallister, who he executed after a short siege.
Brynden married Alicent Baelish at King Damon's behest, building an immediate enmity with her, as well as her beloved Walder Bracken. To reign in the future lord, Brynden married his sister to him, as well as giving him orders to oversee the construction of the Kingsroad, which was being repaired after years of substandard maintenance.
Brynden traveled to Harrenhall, to meet with Tion Lannett about the mistreatment of some of Brynden's lesser vassals.
Brynden also made a request to the High Septon to have his marriage formally annulled. Ultimately the plea fell on deaf ears and he and Alicent were condemned to further unhappiness in each others company.
Upon the death of Sansa Baelish, Alicent's mother, Brynden allowed his wife to leave to bury their mother at their ancestral seat, Harrenhal. During the funeral Walder Bracken and his men set upon Brynden's retinue lead by Bradamar Frey. They were all killed and represented the first act of violent hostilities between the two feuding houses.
Alicent Baelish named herself Lady of the Riverlands and Walder Bracken set out to begin the fighting. He began a campaign of guerilla warfare against the smallfolk of the Riverlands, notably sacking the town of Pennytree. In response, Brynden called upon his levies and set out for war. At the same time, he petitioned the High Septon to annul his marriage once more. This time (and having seen the outbreak of actual fighting between the couple) the request was granted.
Brynden's forces were delayed by house Darry. While they weren't technically fighting for Walder they attempted to use their strategic position at a crossing to manipulate Brynden into accepting a marriage proposal. Brynden, angered by his vassal attempting to gain personal power in the midst of a civil war, denied the request and instead went west to Riverrun.
At Riverrun Brynden learned that the house's heir, Mathis Tully, died fighting Walder's men. The Tully liege, Benedict Tully, swore his allegiance to Brynden and vowed to raise his own levies to join the fighting. He also made a marriage offer of his own, offering his second daughter's hand to Brynden. This time Brynden accepted and was wed to Celia Tully in a hastily arranged wedding.
“There will always be dissenters in your Kingdom, My Lord. My father taught me that. There will always be one or another, who hates you for no reason, or resents you… “ Like me. “Who would seek to topple everything you are and everything you stand for. And when they’re caught, they cower. I wonder, are you a just man, Lord Frey? Given that one of your loyal vassals turns coat and declares you an enemy to the realm, what do you do, once you’ve won? Do you cut off his hands? Send him to the wall? Execute him? Let him off with a stern warning? What kind of man are you, Lord Frey? Save for the kind of man that would rather dishonor a woman’s wishes.” - Alicent Frey to Brynden
Randyll Frey, father (deceased)
Belandra Frey, mother (deceased)
Alester Frey, brother (deceased)
Tywin Frey, brother (deceased)
Alyssa Frey, sister
Edwin Frey, Uncle
Addam Frey, First Cousin Once Removed