His first marriage, in or before 1289, was Eleanor de Gorges. His second wife was Joan, widow of Nicholas de Percy and daughter and heir of Sir Walter Foliot his wife Ada or Alda, daughter and heir of Sir Laurence de Samford of Melbury.
By his second wife, Sir John had three daughters, Alice, Joan and Elizabeth.
He was summoned for military service abroad in May, 1297, to the muster at Carlisle June 24, 1300, for service against the Scots, and again in 1301 and in 1302.
in 1316 and 1317 he was in Ireland, serving against Edward Bruce, and in February 1324 or 1325 was summoned for service in Guienne. He and his son John were both knighted, 22 May 1306, at the knighting of Prince Edward.
He was a conservator of the peace in Dorset, 1307-1329. In May 1324 he was summoned to attend the Great Council at Westminster. In the political troubles of the reign of Edward II he took the King's side, while his son John was an adherent of Thomas, Earl of Lancaster.
His son John Maltravers, with Thomas Berkeley, was charged with keeping Edward II prisoner in Berkeley Castle in 1327 after Edward was captured by his enemies. They were give five pounds a day for Edward's maintenance. Edward is said to have died during the night of September 21. Historians generally argue that Edward probably was murdered, and the younger John Maltravers is suspected along with Sir Thomas Gurney and William Ockley.