From the longer Wikipedia page 
John de la Pole, 2nd Duke of Suffolk, KG (27 September 1442 – between 29 October 1491 and 27 October 1492), known as "the Trimming Duke". He was the son of William de la Pole, 1st Duke of Suffolk and Alice Chaucer, daughter of Thomas Chaucer.
Sometime before February 1458, John married Elizabeth, the second surviving daughter of Richard of York and Cecily Neville. She was the sister of Edward IV and Richard III. John was thus brother-in-law of two Kings of England.
The Dukedom of Suffolk had been forfeited when John's father was executed. The title was restored by Edward IV, and John was created Duke of Suffolk by Letters Patent on 23 March 1463. He was Constable of Wallingford Castle and held the Honour of Wallingford. In 1472 he was made a Knight of the Garter and appointed High Steward of Oxford University. He was also sometime Lord Lieutenant of Ireland.
His sons included John de la Pole, 1st Earl of Lincoln (c. 1462-16 June 1487). He was designated heir to his maternal uncle Richard III and Edmund de la Pole, 3rd Duke of Suffolk (1471-30 April 1513). Yorkist pretender in succession to his brother John.