Sir Thomas was the second son of Reginald de Cobham, de jure 3rd Baron Cobham by his first wife, Eleanor, daughter of Sir Thomas Culpeper.
He was also the brother of Eleanor Cobham, who was the wife of Humphrey, Duke of Gloucester and accused of treasonable necromancy against Henry VI.
Sir Thomas succeeded to the family estates on the death, s.p., of his niece, Margaret Neville, Countess of Westmorland (née Cobham).
14 April 1472, bur Lingfield, Surrey), daughter of Humphrey Stafford, 1st Duke of Buckingham and Lady Anne Neville, and widow (married firstly April 1460) of Aubrey Vere, JP (died beheaded Tower Hill, London, 20 February 1462, interred at Austin Friars, London), a son of John de Vere, 12th Earl of Oxford.
[4] Cobham died in 1471, without legitimate male issue, and was buried at Lingfield, Surrey.