From A Wiki of Ice and Fire
Master-at-arms at Dragonstone
|Allegiance|| House Corbray|
|Book(s)||The Sons of the Dragon (mentioned)|
On the account of his reputation as one of the deadliest knights in the Seven Kingdoms, Ser Gawen was chosen by Queen Visenya Targaryen as master-at-arms for her son, Prince Maegor Targaryen, on Dragonstone.