Thomas was the eldest son of Gilbert Bullock of Arborfield Hall and his wife, Elizabeth (alias Margaret), the eldest daughter of Sir William Norreys of Yattendon Castle. During his early years, Thomas was described as 'of Hampshire' and a residence seems to have been acquired in that county for his use during his father's lifetime, and before he succeeded to the Arborfield estates some time between 1504 and 1514. This was probably the land in Stratfield Saye mentioned in his will. Around the time of his succession, Thomas married a close neighbour whom he must have known from childhood. Alice was the daughter of John Kingsmill of Langley Pond Manor in Barkham, and also of Freefolk in Hampshire. Her father was a Justice of the Court of Common Pleas in the reign of King Henry VIII and may have helped his son-in-law’s rise at court, where, in 1516, Thomas was appointed a Gentleman Usher Extraordinary to the King. He would thus have spent much time attending the monarch in one of his London palaces or at Windsor Castle. Although, Berkshire was still his family home and, in 1518 and 28, he was Escheator (or Crown agent) for Oxfordshire and Berkshire, as well as being one of the Commissioners for the Berkshire Court appointed to collect the subsidy which was levied by King Henry in 1523.

Having had at least six sons, Thomas himself had to make many land provisions similar to his father’s and, in the year 1542, there is a record that he leased, for forty years, the manor of Wokefield, as well as lands in Stratfield Mortimer. We find his younger sons, George, William & Gilbert, seated at these two places only thirteen years later. He was no less generous to his King and, in 1544, was returned among the nobles and gentry of England who supplied men and horses for the war with France. Thomas' contingent consisted of "archers eight, and billmen thirteen" along with additional horse harnesses. As a change was made, about this time, in the family crest, it is not improbable that the 'seven billhooks' of the new version were granted to him in allusion to this martial aid to his sovereign in time of war.