When his elder brother, John Sydenham of Combe, died without male children, Humphrey inherited the paternal estates. John Sydenham had married Margery Poulet, daughter of Sir Anthony Poulett (1562--1600) (alias Paulet), of Hinton St George, Somerset, Governor of Jersey, and Captain of the Guard to Queen Elizabeth. Her brother was John Poulett, 1st Baron Poulett (1585--1649).
Margery Poulet
Queen Elizabeth