From A Wiki of Ice and Fire
|Book(s)|| A Storm of Swords (Mentioned)|
A Feast for Crows (Mentioned)
A Dance with Dragons (Mentioned)
Willas Tyrell is the eldest son and heir of Lord Mace Tyrell and Lady Alerie Hightower. Though crippled with a bad leg, he is often noted as a studious, educated, and kind, and is renowned for breeding the finest hawks, hounds, and horses in the Seven Kingdoms.
Willas Tyrell was borne the eldest son Lord Mace Tyrell and Lady Alerie Hightower, heir to Highgarden. During his first tourney, he was competing against Prince Oberyn Martell of Dorne, who knocked Willas from his horse. Unfortunately, his foot caught in his stirrup as he fell, and he pulled his horse on top of him, crushing his leg and leaving him a cripple.
Though the incident fanned the flames of the considerable enmity between Houses Tyrell and Martell, Willas bore Oberyn no personal ill will and the two long remained in correspondence, sharing a passion for horseflesh. Ever since his accident, Willas has occupied himself with scholarly studies. He was regarded as a much more capable leader than his father. His Grandmother despite having a low opinion of her son has a very high opinion of her grandson WIllas.
A Storm of Swords
Olenna Redwyne plots to have Sansa Stark married to Willas. Sansa readily accepts the offer, but it is foiled after she reveals the the plot to Dontos in the godswood. Tywin Lannister learns of the plot from Petyr Baelish and hastily marries Sansa to his son Tyrion. Tywin offers Cersei Lannister to be married to Willas, which would quieten rumours of her incest with Jaime, but the Tyrells refuse the offer.
A Feast for Crows
After the Battle of the Shield Islands, Willas reportedly sent messengers to Lord Leyton Hightower ordering him to strengthen his defences in Oldtown. Willas also guessed (correctly) that the Ironborn did not follow the coast when attacking the shields so the ambush would take the lords of the shields off guard.