Jan married Princess Elizabeth Plantagenet, Countess of Hereford and Essex on 18 Jan 1297 in Ipswich Priory Church, Suffolk, England. Elizabeth (daughter of Edward Plantagenet, King Edward I of England and Eleanor of Castilla) was born on 5 Aug 1282 in Rhudlan Castle, County Carnarvon, Wales; died on 5 May 1316 in Quendon, Essex, England; was buried on 23 May 1316 in Walden Abbey, Essex, England. [Group Sheet] [Family Chart]