His father died while FitzWilliam was in his infancy, and his mother remarried Sir Anthony Browne senior so that William was half-brother to Sir Anthony Browne. Probably as a result of this connection, he was chosen as a companion for Henry, Prince of Wales (later King Henry VIII) and brought up alongside him. After King Henry's coronation in 1509, he was made a Gentleman Usher and King's Cupbearer, and gradually rose at Court. He began his military career at sea, serving under the Marquess of Dorset in 1512 and Sir Edward Howard in the disastrous second attack on Brest. Unlike his commander, he escaped the debacle, but was badly injured by a crossbow bolt. He had recovered sufficiently to accompany the King into France as an Esquire of the Body, and was knighted on 25 September 1513, the