A knight of House Darry and, by semi-canon account, brother to Ser Jonothor of the Kingsguard, Willem served as master-at-arms of the Red Keep under King Aerys II Targaryen—chosen for the post over Lord Tywin Lannister's brother Ser Tygett—and trained the young Prince Rhaegar Targaryen when the boy resolved to become a knight. Staunchly loyal to House Targaryen, he was sent with Queen Rhaella and Prince Viserys to Dragonstone after Rhaegar's death at the Trident. When the garrison there weighed selling the royal children to Robert Baratheon, Willem and four loyal men broke into the nursery and bore the infant Princess Daenerys and her brother away by night to Braavos, settling them in a house with a red door. There he signed a pact with Prince Oberyn Martell pledging Viserys to Princess Arianne, before a wasting sickness took him when Daenerys was about five, in 289 or 290 AC; she remembered him ever after as a gentle, sweet old bear. With his death the servants stole the children's coin and turned them into the streets.

Family
- Parents
- Lord Darry, Lady Darry
