He was betrothed to Catelyn Tully , but was executed in King's Landing alongside his father by the Mad King when he entered the Red Keep with a handful of companions (Jeffory Mallister, Kyle Royce, Ethan Glover, and Elbert Arryn) demanding that Crown Prince Rhaegar Targaryen answer for his supposed abduction of Lyanna. The five young men were arrested by King Aerys II and charged with treason. Their fathers were called to King's Landing to answer these charges as well but were apprehended on arrival and presented in front of the court in the Red Keep.
Lord Rickard was tied to a stake and Brandon to a strangulation device. Brandon strangled himself reaching for a sword inches away from him in attempt to rescue his father, who was burned alive by wildfire in front of him, on orders of the Mad King, who died first is unclear.
After Brandon's death, Catelyn married Eddard instead. Brandon was buried with the Kings of Winter in the crypt beneath Winterfell.