
The size ofKing Arthur's family mirrored the size of his legend. Although always large, it particularly grew as the legend ofKing Arthur gained popularity throughoutBritain. According to the earliest Welsh Arthurian tradition, Arthur has an extensive family network. This includes his parentsUther Pendragon andEigyr (Igraine), his wifeGwenhwyfar (Guinevere), his nephewGwalchmei (Gawain), abrother, andseveral sons. His maternal lineage is also detailed, which includes his grandfatherAmlawdd Wledig, a legendary king. His family tree was both simplified and expanded in shared British and French traditions. The two countries added characters from other medieval European chronicles and romances, which introduced new characters, such as Arthur's half-sisters, includingMorgan, and their children, includingMordred. Various rulers claimed to be descended from Arthur, in particular theHouse of Tudor and Scottish clans, reflecting the importance of his family legend in medieval and early modern genealogies.

In Welsh Arthurian pre-Galfridian tradition, Welsh sources laid out a few close familial figures; Arthur had a father namedUther Pendragon, a brother calledMadog, and a nephew (Eliwlod).[1] Arthur also appears to have had a sister in this tradition. She is unknown except in reference toGwalchmei, son of Gwyar, who is said to be the child of Arthur's cousin and sister inCulhwch and Olwen. TheVita Iltuti and theBrut Dingestow both say that Arthur's mother was namedEigyr.[2]Culhwch and Olwen also names a half-brother, Gormant, the son of Arthur's mother andRicca, the chief elder ofCornwall. This parallels later stories ofGorlois,Duke of Cornwall.[3]
The 13th-century genealogies inMostyn MS. 117 lay out Arthur's ancestry in detail. He is the son ofUthyr, the son of Custennin, the son of Cynfawr, the son of Tudwal, the son of Morfawr, the son of Eudaf, the son of Cadwr, the son of Cynan, the son ofCaradoc, the son ofBran, and the son ofLlŷr. Regarding Arthur's own family, his wife is consistently said to beGwenhwyfar. She is usually stated to have a sister namedGwenhwyfach and to be the daughter of KingOgrfan Gawr (who is sometimes called 'Gogrfan Gawr' or '[G]Ogrfan the Giant').Culhwch andBonedd yr Arwyr also indicate that Arthur had some sort of relationship with Eleirch, daughter of Iaen, resulting in a son named Kyduan (Cydfan).[4] Kyduan is not Arthur's only child in Welsh Arthurian tradition – he is also said to have sons named Amr (Amhar),[5] Gwydre,[6] Llacheu[7] and Duran.[8] (See theOffspring section for further information about Arthur's children.)
In addition to this immediate family, Arthur was said to have had a great variety of distant relatives, including maternal aunts, uncles, and cousins, as well as a grandfather namedAnlawd (or Amlawdd) Wledig ("Prince Anlawd"). Anlawd is the common link between Arthur and many of these figures. For example, the relationship between first cousins (implied or stated), between Arthur,Culhwch,Illtud, andGoreu fab Custennin, depends on all of their mothers being children of Anlawd. Arthur's maternal uncles inCulhwch and Olwen, including Llygatrud Emys, Gwrbothu Hen, Gweir Gwrhyt Ennwir, and Gweir Baladir Hir, are similarly related through Anlawd.[9] Some argue that Anlawd only exists as a means to allow medieval Welsh authors to interconnect figures with Arthur by acting as a genealogical link.[10]

Geoffrey of Monmouth carried over relatively few members of Arthur's family in the Welsh materials. Arthur's grandfather, Anlawd Wledic, and his maternal uncles, aunts, and cousins do not appear there, nor do his paternal relatives or any of his sons. Only the core family seems to have made the transition in Geoffrey's influential version: Arthur's wife Gwenhwyfar (who becameGuinevere), his father Uthyr (Uther), his mother Eigyr (Igerna), and his nephew Gwalchmei (Gawain). Uther was given a new family, including two brothers and their father.[11] Gwalchmei's mother, Gwyar, instead became Anna, who was married toLoth, while Modredus (Mordred) became her second son (he was not her son under Welsh tradition, bearing the name Medraut). As many writers based their stories on Geoffrey's work, it was his version that remained popular, rather than traditional Welsh family trees.[12]

In thechivalric romance branch of such common tradition, Arthur gains a sister or half-sister namedMorgan, first identified as his relative byChrétien de Troyes'Yvain.[13] Arthur's other sister or half-sister, today best known asMorgause, is a daughter of Gorlois and Igerna (Igraine). She replaced Anna in the romances as the mother of Gawain and Mordred. She and Morgan may also be joined by a third half-sister, today best known asElaine. Drawing on earlier sources,Richard Carew mentions another sister of Igraine and Uther, named Amy.[14] The overall number of Arthur's sisters or half-sisters varies between the different romances, ranging from as few as one or two to as many as five (in which case one of them may die early).[15] Their names and roles also vary, as do their husbands (most commonly the British kingsLot,Urien, andNentres, who are largely interchangeable).[a] Through his sisters, Arthur is given further nephews, who all become members of theRound Table. The sisters usually (but not always) have particular children in the romances. In popular tradition of the prose cycles, Morgause has Gawain,Agravain,Gaheris, andGareth; Elaine hasGaleschin; and eitherMorgan or a fourth sister hasYvain. Other romance authors such as Chrétien[17] andWolfram von Eschenbach[18] mention or feature Arthur's nieces and occasionally additional nephews (for example,Lancelot is the son of Arthur's unnamed sister inUlrich von Zatzikhoven'sLanzelet, but nowhere else).
Arthur's son, namedLoholt, was introduced inChrétien de Troyes'sErec and Enide.[19] He is possibly based on one of Arthur's sons from Welsh tradition, Llacheu.[20] Geoffrey turnsAmbrosius Aurelianus, the historical Romano-British leader, into Uther's brother. He also derives Arthur's lineage from the self-proclaimed Western Roman EmperorConstantine III of Britain, presenting him as Arthur's grandfather. Additionally, the chronicleBrut Tysilio makesCador, son of Gorlois Arthur's half-brother, sharing Igraine as a mother.[21] In Geoffrey'sHistoria, Cador's sonConstantine succeeds Arthur as the high king of Britain. One important figure with no actual blood relation to Arthur isEctor, who is featured as a secret foster-father of Arthur in much of the romance tradition, along with Ector's sonKay as the young Arthur's foster-brother.
Although Arthur is given sons in both early and late Arthurian tales, he is rarely has many generations of offspring. This is at least partly because of the usually premature deaths of Arthur's sons. In some cases, including inLe Morte d'Arthur,[22] Arthur's failure to produce a legitimate heir contributes to his fall.
In the early Welsh tradition, Mordred (Medraut) was a nephew of Arthur, before later becoming Arthur's child. In this tradition Mordred three different sons, however, their stories are largely lost.
Amr is the first of Arthur's sons to be mentioned in Arthurian literature, appearing in the 9th-centuryHistoria Brittonum:
There is another wonder in the region which is called Ercing. A tomb is located there next to a spring which is called Licat Amr; and the name of the man who is buried in the tomb was called thus: Amr. He was the son of Arthur the soldier, and Arthur himself killed and buried him in that very place. And men come to measure the grave and find it sometimes six feet in length, sometimes nine, sometimes twelve, sometimes fifteen. At whatever length you might measure it at one time, a second time you will not find it to have the same length – and I myself have put this to the test.[23]
Why Arthur chose or was forced to kill his son is never made clear. The only other reference to Amr comes in the post-Galfridian Welsh romanceGeraint, where "Amhar son of Arthur" is one of Arthur's four chamberlains, along withBedwyr's son Amhren.[24]: 231 Another son, Gwydre, suffers a similarly premature death, being slaughtered by the giant boarTwrch Trwyth inCulhwch and Olwen, along with two of Arthur's maternal uncles. No other references to either Gwydre or Arthur's uncles survive.[25][24]: 132, 134 The third son, Duran, known only from a possibly 15th-century Welsh text, is said to have died on the field ofCamlann.[26]
More is known about Arthur's son Llacheu. He is one of the "Three Well-Endowed Men of the Island of Britain", according toTriad 4, and he fights alongsideCei in the early Arthurian poemPa gur yv y porthaur?.[27] Like his father is inY Gododdin, Llacheu frequently appears as a heroic figure in early Welsh literature, and is also appears in local folklore lied to specific locations.[28] Because of this, there is general consensus that Llacheu was a relatively major character in early Arthurian mythology.[29] Nonetheless, Llacheu too dies, with the speaker in the pre-Galfridian poemYmddiddan Gwayddno Garanhir ac Gwyn fab Nudd remembering that he had "been where Llacheu was slain / the son of Arthur, awful in songs / when ravens croaked over blood."[30] The romance character based on him, known asLohot or similar names, usually also dies young.
Mordred is a major exception to this tradition of Arthur's sons dying childless. According to Geoffrey of Monmouth and the post-Galfridian tradition, Mordred (like Amr) is killed by Arthur, this time dying at Camlann. However, unlike the others, he hastwo sons, who both rose against Arthur's successor and cousinConstantine III with the help of the Saxons. However, in Geoffrey'sHistoria (where the motifs of Arthur's killing of Mordred and Mordred's sons first appear), Mordred was not Arthur's son.[31] His relationship with Arthur was reinterpreted in theVulgate Cycle, as he was made the result of an unwitting incest between Arthur and his sister.[32] This tale is preserved in the later romances, so by the time of thePost-Vulgate Cycle, a tale emerges whereMerlin tells Arthur that Mordred would grow up to destroy him. In this story, Arthur devisesHerod-like plot to rid of all of his children on the same day to try to save himself from this fate.[33] The Post-Vulgate version also features another of Arthur's illegitimate sons,Arthur the Less, who survives for as long as Mordred but remains fiercely loyal to Arthur.
Other literature further expanded Arthur's immediate family. His daughter, Archfedd, is found in only one Welsh source, the 13th-centuryBonedd y Saint.[34] A daughter named Hild[e] is mentioned in the 13th-century IcelandicÞiðreks saga (Thidrekssaga), while theMöttuls saga from around the same period features a son of Arthur named Aristes. Arthur's son, Samson the Fair, for whom the Norse storySamsons saga fagra is named, also has a sister named Grega. Rauf de Boun's 1309Petit Brut lists Arthur's son Adeluf III as a king of Britain, also mentioning Arthur's other children, Morgan le Noir (Morgan the Black), and Patrike le Rous (Patrick the Red) by an unnamedFairy Queen.[35] Later on, a number ofearly modern works have occasionally give Arthur more or different sons and daughters.[b]
A supposed direct lineage from King Arthur has been professed by some English monarchs, especially those of Welsh descent, among them the 15th-centuryKing Henry VII (throughCadwaladr ap Cadwallon),[36] who even namedhis first-born son after Arthur, and the 16th-centuryQueen Elizabeth I.[37] In theScottish Highlands, the descent from King Arthur remains included in rival genealogies of bothClan Arthur (MacArthur) andClan Campbell,[38] whose traditions involve Arthur's son, variably known as Merbis, Merevie, Smerbe, Smerevie, or Smereviemore.[39][40] InIberia, medieval and early modern genealogies attributedQueen Baddo, wife of the 6th-centuryVisigothic KingReccared I, as a daughter of King Arthur.[41]