John's father augmented the family's position by exploiting the favour of the King, Henry VI, to whom he was an important councillor in the 1440s. Already Earl of Suffolk, John's father was in turn elevated to a marquess (in 1444) and then Duke of Suffolk (1448), and with these titles received major grants from the crown. Also, it had been his father's receipt of the wardship of Margaret Beaufort from the king that enabled John's marriage to her, whilst both were still infants and despite them being within the prohibited degrees of consanguinity. Contemporaries claimed that the marriage to the daughter of John Beaufort, Duke of Somerset (cousin of the-then childless king) was intended to make John de la Pole an eventual heir to the crown; this is considered unlikely by modern historians, who have pointed at indications that the King supported William in these plans. It has been suggested that the marriage was the direct result of William's political difficulties during the 1450-1 parliament.