Willem Frey

Willem Frey is an unseen character mentioned in the second season. He is a member of House Frey whose wedding was celebrated with a tournament some time before the series began.

Season 2
Ser Alton Lannister recalls squiring for his distant cousin Ser Jaime Lannister at the tournament. Jaime defeated Ser Balon Swann. The day was one of Alton's proudest achievements and he was disappointed when he had to leave the field to eat at the periphery of the wedding feast.

In the books
In the A Song of Ice and Fire novels there is no character of this name.