Gorlois was a Duke

Legendary Dukes of Cornwall

"Duke of Cornwall" appears as a title in pseudo-historical authors as Nennius and Geoffrey of Monmouth. The list is extremely patchy, and not every succession was unbroken. Indeed, Geoffrey repeatedly introduces Dukes of Cornwall only to promote them to the Kingship of the Britons and thus put an...

 of Cornwall

Cornwall

Cornwall is a unitary authority and ceremonial county of England, within the United Kingdom. It is bordered to the north and west by the Celtic Sea, to the south by the English Channel, and to the east by the county of Devon, over the River Tamar. Cornwall has a population of , and covers an area of...

 and Igraine

Igraine

Igraine , in Arthurian legend, is the mother of King Arthur. She is also known in Latin as Igerna, in Welsh as Eigyr, in French as Igerne, in Thomas Malory's Le Morte d'Arthur as Ygrayne— often modernized as Igraine—and in Wolfram von Eschenbach's Parzival as Arnive...

's first husband before her marriage to Uther Pendragon

Uther Pendragon

Uther Pendragon is a legendary king of sub-Roman Britain and the father of King Arthur.A few minor references to Uther appear in Old Welsh poems, but his biography was first written down by Geoffrey of Monmouth in his Historia Regum Britanniae , and Geoffrey's account of the character was used in...

, according to the Arthurian legend. Later versions give him a number of children, the most famous of which are Elaine

Elaine (legend)

Elaine is a name shared by several different female characters in Arthurian legend.-Elaine of Astolat:Elaine of Astolat, also known in some texts as Elaine the Fair or the Fair Maid of Astolat and as The Lady of Shalott in Lord Alfred Tennyson's same-titled poem, is a maiden who falls in unrequited...

, Morgause

Morgause

Morgause , known in earlier works as Gwyar or Anna, is the sister or half-sister of King Arthur in the Arthurian legend. In her earliest appearance she is Arthur's full sister by Uther Pendragon and Igraine; Gwyar is her name and she is the mother of Gwalchmei...

 or Anna, and Morgan le Fay

Morgan le Fay

Morgan le Fay , alternatively known as Morgane, Morgaine, Morgana and other variants, is a powerful sorceress in the Arthurian legend. Early works featuring Morgan do not elaborate her character beyond her role as a fay or magician...

.

According to Geoffrey of Monmouth

Geoffrey of Monmouth

Geoffrey of Monmouth was a cleric and one of the major figures in the development of British historiography and the popularity of tales of King Arthur...

's Historia Regum Britanniae

Historia Regum Britanniae

The Historia Regum Britanniae is a pseudohistorical account of British history, written c. 1136 by Geoffrey of Monmouth. It chronicles the lives of the kings of the Britons in a chronological narrative spanning a time of two thousand years, beginning with the Trojans founding the British nation...

, Uther falls in love with Igraine and wars with Gorlois to get to her. Uther asks for Merlin

Merlin

Merlin is a legendary figure best known as the wizard featured in the Arthurian legend. The standard depiction of the character first appears in Geoffrey of Monmouth's Historia Regum Britanniae, written c. 1136, and is based on an amalgamation of previous historical and legendary figures...

's aid in pursuing her, and Merlin concocts some drugs that disguise Uther in the form of Gorlois. As Gorlois, he approaches his love easily and they sleep together, conceiving Arthur

King Arthur

King Arthur is a legendary British leader of the late 5th and early 6th centuries, who, according to Medieval histories and romances, led the defence of Britain against Saxon invaders in the early 6th century. The details of Arthur's story are mainly composed of folklore and literary invention, and...

. Unbeknownst to either of them, the real Gorlois has been killed in his castle that very night. Eventually Igraine is convinced to marry Uther.

Later treatments such as the Vulgate Cycle and Sir Thomas Malory

Thomas Malory

Sir Thomas Malory was an English writer, the author or compiler of Le Morte d'Arthur. The antiquary John Leland as well as John Bale believed him to be Welsh, but most modern scholars, beginning with G. L...

's Le Morte d'Arthur

Le Morte d'Arthur

Le Morte d'Arthur is a compilation by Sir Thomas Malory of Romance tales about the legendary King Arthur, Guinevere, Lancelot, and the Knights of the Round Table...

expand on this outline by having Gorlois' daughters married off to Uther's vassals; Elaine to King Nentres, Morgause to King Lot

King Lot

Lot or Loth is the eponymous king of Lothian in the Arthurian legend. He is best known as the father of Sir Gawain. Such a ruler evidently first appeared in hagiographical material concerning Saint Kentigern , which feature a Leudonus, king of Leudonia, a Latin name for Lothian...

, and after receiving an education in a convent

Convent

A convent is either a community of priests, religious brothers, religious sisters, or nuns, or the building used by the community, particularly in the Roman Catholic Church and in the Anglican Communion...

, Morgan to King Urien

Urien

Urien , often referred to as Urien Rheged, was a late 6th century king of Rheged, an early British kingdom of the Hen Ogledd . His power and his victories, including the battles of Gwen Ystrad and Alt Clut Ford, are celebrated in the praise poems to him by Taliesin, preserved in the Book of Taliesin...

. Arthur is spared any knowledge of this when he is whisked away by Merlin to be raised by Sir Ector

Sir Ector

Sir Ector is the father of Sir Kay and the foster father of King Arthur in the Arthurian legend. Sometimes a king instead of merely a lord, he has an estate in the country as well as properties in London. In The Once and Future King T. H...

.