John Beaufort, Marquis of Somerset, b. ca 1370; d. 16 Mar. 1409/10; m. before 28 Sep. 1397, Margaret de Holland (47-33), d. 30 Dec. 1439; she m. (2) Thomas Plantagenet, Duke of Clarence. (G. E. Cokayne’s (new revised) “Complete Peerage,” vols. I-XII pt. 2, 1910-1959 - IV, 416; VII, 415; XII pt. 1, 39-45).55