Robert De Boron
In Robert de Boron's later Merlin, Igraine's previous husband is an unnamed Duke of Tintagel and it is by him that she becomes the mother of two unnamed daughters. One marries King Lot and by him becomes the mother of Gawain, Mordred, Gaheriet and Guerrehet. A second daughter, also unnamed in some variants but in some named Morgaine, is married to a certain King Nentres of Garlot. A third illegitimate daughter of the Duke of Tintagel is sent to a school and there learns so much she becomes the great sorceress Morgan le Fay.
In fact Morgan and Morgaine are respectively the nominative and oblique forms of the same name. Indeed no accounts outside of de Boron's Merlin mentions that Morgan le Fay is illegitimate and therefore in this version Arthur's stepsister. According to Robert de Boron, Igraine died before her second husband.
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