Youngest son of Mace Tyrell, Lord of Highgarden, and Alerie of House Hightower, born at Highgarden in 282 AC and brother to Ser Willas, Ser Garlan, and Margaery. Sent in boyhood to squire at Storm's End for Lord Renly Baratheon, where he grew tall and lithe and uncommonly comely, and where he and Renly became true love and paramour, a bond the singers passed over but the court knew well. Knighted at sixteen and famed thereafter as the Knight of Flowers for the blooms he wore and the rose of Highgarden upon his shield, he rode a string of tourney victories the length of the Reach.
At the Hand's tourney in King's Landing in 298 AC he unhorsed Ser Gregor Clegane on a mare in heat, a stratagem that nearly cost him his throat when the Mountain hewed off his horse's head and was driven from the lists only by Sandor Clegane's intervention. He yielded the champion's purse to the Hound and then, riding past the gallery, plucked a red rose from his crown and laid it in Sansa Stark's lap, a gesture she carried in her heart through every cruelty after. When the war came he rode south with Renly's host and was named to the Rainbow Guard as its Lord Commander, but he was absent from Renly's pavilion at Bitterbridge the dawn his king was slain by a shadow, and finding Brienne of Tarth standing over the body he drew steel against her in his grief before the Tyrells withdrew to Bitterbridge and then to Highgarden, where his sister was offered to King Joffrey and his House to Lord Tywin.
He fell upon Stannis Baratheon's host at the Battle of the Blackwater at the head of the Tyrell van, clad in the green armor of Renly's ghost with antlered helm and rose-and-stag banners, and broke the Baratheon lines against the river while his brother Ser Garlan rode another wing. For that day's work the Iron Throne raised him to the Kingsguard, and his sworn white cloak passed Highgarden to Willas. He sailed thereafter against Dragonstone to root out the last of Stannis's garrison under Ser Rolland Storm, and in storming the castle's walls he took grievous wounds from boiling oil and crossbow bolts, hurts the realm whispered would either kill him or unmake the Knight of Flowers for good.