He came to Dublin in about 1308: his father lived in Ireland for some years, managing the Earl of Pembroke's Irish estates, and it is possible that John was born in Ireland. He married Alice de Morton, daughter and co-heiress of Geoffrey de Morton, who was Lord Mayor of Dublin and one of the city's wealthiest shipowners and his wife Matilda or Maud de Bree, widow of Robert de Bree: they had at least one son, John, commonly known as John of Granchester. The younger John was an adult by 1342.Ball pp.26-31
