Troy Tyrell was the son and heir of Lord Paramount Baelor Tyrell. He was killed by his younger brother, Benjen, in a duel forced upon them by their capture, Thaddius Lannister, during the Ascent of the Lion.
Troy Tyrell was raised at Highgarden in the Reach and groomed to assume the Lord Paramountcy, while his twin brother Olyvar Tyrell chose to join the Citadel. He was rumored to be in an incestuous relationship with his sister, Maude Tyrell. As children, Troy, Olyver, and Maude were close friends.
Troy marched with King Harys Baratheon to Oldtown when his sister was kidnapped and rumored to be held there. In a fit of rage, he grabbed Lord Gylen Hightower and shoved him against a wall, breaking Guest Right and causing Lord Hightower to demand that the King and his men leave his city.
Once they heard that the capital was sacked, the King's army marched to Highgarden to muster the Tyrell forces and take back the throne. Along the way, Thaddius Lannister of the Kingsguard betrayed the Harys and took Troy hostage, along with his younger siblings Benjen and Mellara Tyrell. On the way to King's Landing, Thaddius forced Troy and Benjen to duel to the death. Benjen decapitated Troy. Ser Thaddius forced Benjen to carry Troy's head back to the capital on his lap.
Baelor Tyrell, father (deceased)
Olyvar Tyrell, brother
Maude Tyrell, sister (deceased)
Benjen Tyrell, brother (deceased)
Meredyth Tyrell, sister
Mellara Tyrell, sister (deceased)