succeeding his second cousin, John de Vere, 14th Earl of Oxford, in the earldom. De Vere had two stepbrothers, William Courtenay and Walter Courtenay, and a stepsister, Katherine Courtenay, by his mother's second marriage, before 1491, to Sir Walter Courtenay (d. 7 November 1506), a younger son of Philip Courtenay of Powderham, Devon, by Elizabeth Hungerford.

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