Sir Oliver St. John, of Penmark, co. Glamorgan, (of the family of St. John of Stanton St. John), m. Margaret,* dau. of Sir John de Beauchamp, and sister and heir of John, Lord Beauchamp, of Bletshoe, and had two sons, viz., John, his heir, and Oliver. [Sir Bernard Burke, Dormant, Abeyant, Forfeited, and Extinct Peerages, Burke's Peerage, Ltd., London, 1883, p. 46, St. John, Earls of Bolingbroke]
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