Thomas Courtenay, 6th/14th Earl of Devon, was the eldest son of Thomas de Courtenay, 5th/13th Earl of Devon, by his wife Margaret Beaufort, the daughter of John Beaufort, 1st Earl of Somerset, and Margaret Holland, daughter of Thomas Holland, 2nd Earl of Kent. Through his mother, he was a great-great-grandson of King Edward III. The ordinal number given to the early Courtenay Earls of Devon depends on whether the earldom is deemed a new creation by the letters patent granted 22 February 1334/5 or whether it is deemed a restitution of the old dignity of the de Redvers family. Authorities differ in their opinions, and thus alternative ordinal numbers exist, given here.