On 10 February 1604, Lettice Knollys, Dowager Countess of Leicester, filed a bill in the Court of the Star Chamber against Sir Robert Dudley, the illegitimate but acknowledged son of her second husband Robert Dudley, 1st Earl of Leicester. Dudley, also known as "Robin Sheffield", had disputed that he was not of illegitimate birth, but rather that he was born from a legal union between his parents - Leicester and his one time paramour Douglas Howard, Lady Sheffield.

Thomas Seymour was born in c.1508, a younger brother to Edward Seymour, Earl of Hertford and later Duke of Somerset, and older brother to Jane Seymour, Queen of England. Their parents were Sir John Seymour and Margaret Wentworth, and their family seat was Wulfhall, in Wiltshire.