Ralph Arundell married in the reign of Edward 111, Jane, daughter and heiress of Michael Trerise, and thus obtained the estate which his descendants held for the next 400 years. His was a junior branch of the Arundells of Lanherne which was established in the fourteenth century when Sir Oliver, his grandfather married the heiress Margery, daughter and heir of Raynulph de Arundell, Lord of Albominster and Stratton, 2 son of the Earl of Arundell
According to Carew's Survey of Cornwall a Ralph Arundell married Jane/Joan, the daughter of Michael Trerise, during the reign of Edward III. Compare Public Record Office JUST I/1476, mem.73 dorse, July 1367 in which the defendants include Ralph Arundell of Treres and Joan his wife. AR/1/104 is a grant from Sir John Arundell to Ralph Arundell of Trerys in 1358. This Ralph died between July and November 1369 (AR/1/241; AR/32/1 and AR/1/846), and had at least two sons, Nicholas (AR/41/6) and Thomas (AR/41/5), and a daughter Joan (AR/32/1). There is no record of the split in the Lanherne archive and unfortunately the archive of the Arundells of Trerice has disappeared virtually without trace.