Bronn's house

Bronn's House of Highgarden is a Great House of Westeros. It rules over the Reach, a vast, fertile, and heavily-populated region of southwestern Westeros, from their castle-seat of Highgarden as Lords Paramount of the Reach after taking control of the region from House Tyrell following their extinction as a result of the destruction of the Great Sept of Baelor and the Sack of Highgarden.

The house was founded by Ser Bronn of the Blackwater and raised to power as fulfillment of a debt owed by Tyrion of House Lannister, the Hand of the King to the first elected king, Brandon I Stark. The official name, words, and sigil of the house are unknown.

Background
Bronn was a sellsword who first encountered Lord Tyrion Lannister when he was arrested by Catelyn Stark at the Inn at the Crossroads just prior to the War of the Five Kings. Bronn was among the men who traveled with Catelyn as she brought him to her sister, Lysa Arryn, at the Eyrie in the Vale for trial, and Bronn fought and won in a trial by combat for Tyrion. Bronn continued to travel with and work for House Lannister, guarding Tyrion in King's Landing and fighting for him at the Battle of the Yellow Fork and the Battle of the Blackwater. As a result for his heroism at the Battle of the Blackwater, Bronn was knighted as Ser Bronn of the Blackwater.

Ser Bronn was wed to Lady Lollys Stokeworth by Cersei Lannister to strip Tyrion of any potential champions in his trial for the Purple Wedding, but the arrangement was later broken by Jaime Lannister in order to enlist Bronn's aid. Bronn accompanied Jaime to Dorne in an attempt to rescue Myrcella Baratheon, served Jaime at the Second Siege of Riverrun, and fought at the Battle of the Goldroad. Bronn sought a castle and a noble lady as a wife, which Jaime promised him after stripping him of Castle Stokeworth.

After Jaime abandoned his sister, Cersei tasked Ser Bronn with murdering her two brothers for committing treason, promising to give Bronn Riverrun, but Bronn instead negotiated with the Lannister brothers at Winterfell after the Great War ended, threatening to kill them if they didn't follow up on their debts owed to him. Tyrion promised to make Bronn Lord of Highgarden and lord of the Reach if he spared them and they won the war, and Bronn agreed.

Season 8
Bronn's noble house is formally founded when Bronn is raised as the Lord of Highgarden and Lord Paramount of the Reach, a promise made to him by Tyrion Lannister after being blackmailed by Bronn under the threat of death for not paying back debts owed to him.

Members

 * Lord Bronn, knight of the Blackwater, Lord of Highgarden, Lord Paramount of the Reach, and Master of Coin as part of the small council of Tyrion Lannister under King Brandon I Stark.

In the books
In the A Song of Ice and Fire novels by George R.R. Martin, Bronn has not founded his own house. In fact, Bronn's story in the TV series has taken a major deviation from his story in the books. Bronn is still married to Lollys Stokeworth in the books, and thus is still a member of House Stokeworth. House Stokeworth is one of the noble houses of the Crownlands sworn directly to the King of the Andals and the First Men, so Bronn, while elevated to nobility, is far less powerful, certainly not a lord of the Reach. House Tyrell still rules the Reach, but there are still two forthcoming novels, so it is unknown what their ultimate fate is.