Odin's brothers are mysterious figures, rarely seen or mentioned in the surviving sources. From this, we should not infer that they were similarly unknown to the ancient Norsemen. According to Gylfaginning 6, Odin's father, Borr had three sons.
"Straightaway after the rime dripped, there sprang from it the cow called Audhumla; four streams of milk ran from her udders, and she nourished Ymir." Then asked Gangleri: "Wherewithal was the cow nourished?" And Hárr answered: "She licked the ice-blocks, which were salty; and the first day that she licked the blocks, there came forth from the blocks in the evening a man's hair; the second day, a man's head; the third day the whole man was there. He is named Búri: he was fair of feature, great and mighty. He begat a son called Borr, who wedded the woman named Bestla, daughter of Bölthorn (Ymir) the giant; and they had three sons: one was Odin, the second Vili, the third Vé. And this is my belief, that he, Odin, with his brothers, must be ruler of heaven and earth."
That Odin had two brothers named Vili and Ve is confirmed by Lokasenna 26:
"Hold your tongue, Frigg,
you are Fjörgynn's daughter
and have always been eager for men,
for Véi and Vili
you—Viðrir's wife— had
both embraced in your bosom."
—Ursula Dronke translation (1997)
Here the three brothers are called by alliterative names: Vidrir (Odin), Vili and Ve. Snorri, who knew Lokasenna, may have gotten the names of Odin's brothers here.
In Gylfaginning 8, Snorri states that Odin's two brothers helped him slay Ymir. The three brothers use the giant's corpse to create the heavens and the earth. Afterwards, they examine their creation. Gylfaginning 9 reads:
Then said Gangleri: "Much indeed they had accomplished then, methinks, when earth and heaven were made, and the sun and the constellations of heaven were fixed, and division was made of days; now whence come the men that people the world?" And Hárr answered: 'When the sons of Borr were walking along the sea-strand, they found two trees, and took up the trees and shaped men of them: the first gave them spirit and life; the second, wit and feeling; the third, form, speech, hearing, and sight. They gave them clothing and names: the male was called Askur, and the female Embla, and of them was mankind begotten, which received a dwelling-place under Midgard.
Völuspá 17 and 18, a poem well-known to Snorri and one he quotes extensively, says that Askur and Embla were created not by Odin, Vili and Ve but rather by Odin, Hoenir and Lodur:
17. Until three came
out of the company
mighty and loving
Æsir to the house.
They found on land,
Ash and Embla,
18. Breath they had not,
spirit they had not,
no film of flesh nor cry of voice,
nor comely hues.
Breath Óðinn gave,
spirit Hoenir have,
film of flesh Lóðurr gave,
and comely hues.
—Ursula Dronke translation (1997)
Snorri tells us that Odin had 49 names in all, some of which are dramatically revealed in Grímnismál 48-50. In our sources, Thor is known as Hlorridi, Veorr and Asabragi. Likewise Freyja is known as Gefn, Mardöll and Sýr among others. There is no reason to believe that Odin's brothers, like himself, did not have alternate names. Most all mythic characters do. Thus when Völuspá says that Odin, in the creation of man, was assisted by Hoenir and Lodur, and when the Prose Edda (Gylfaginning 9) says that, on this occasion, he was joined by his brothers, who just before (Gylfaginning 6) were called Ve and Vili, then these are only different names of the same powers.
Hoenir and Lodur are Ve and Vili. If the triad of brothers Zeus, Posideon and Hades in Greek mythology are any indication, it would be a mistake to believe that Odin's brothers were mythical ghosts without characteristic qualities, and without prominent parts in the mythological events after the creation of the world and of man, in which we know they took an active part (Völuspá 4, 17, 18). The assumption that this was the case depends simply upon the fact that they have not been found mentioned among the Aesir, and that our fragmentary records, when not investigated thoroughly and with an eye for alternate names, so common in Eddaic poetry, seem to have so little to say concerning them.
In Icelandic and Anglo-Saxon geneologies, Scef is often said to be the son or descendent of Odin. Danish genealogies, however, including Saxo's, which go back further than Skjöld (Scef) make him the son of King Lotherus. There is no doubt that Lotherus, like his descendants, Skjöld (Scef), Halfdan, and Hadding, was taken from the Germanic myth and legend. Saxo Grammaticus, in particular, is well-known for having based his Gesta Dancorum largely on Icelandic mythology. Saxo commonly Latinizes the names and epithets of well-known mythic players. In our mythic records there is only one name of which Lotherus can be a Latinized form, and that name is Lóðurr.
Germanic mythology knows of three divine races: the Aesir, the Vanir and the Alfar (elves). Germanic theogony, as far as we can know, mentions only two progenitors of all the mythological races — the primeval giant Ymir and Buri, the man licked out of the ice by Audumbla. According to Vafþrúdnismál 33, two very different races of giants, spring from Ymir: the offspring of his arms and that of his feet — in other words, the noble race of jötuns to which the Norns, Mimir and Bestla belong, and the treacherous race founded by the six-headed Thrudgelmir. As we have seen, Buri gives rise to Borr, who in turn, by the giantess Bestla, fathers three sons — Odin, Ve, and Vili. Odin is the father and ruler of the Aesir clan. Unless Buri had more sons, the Vanir and Alfar (elf) clans can have no other source than Borr. To this must be added the important observation that Ve and Vili, though brothers of Odin, are never counted among the Aesir proper, and have no halls in Asgard. Odin is the founder of the clan he rules, for this very reason, his brothers cannot be included in his clan, except through adoption. There is every reason to suppose that they, like him, were clan-founders; and as we find two other divine clans besides the Aesir, it stands to reason that Odin's two brothers were their progenitors and clan-chieftains. In other words, Odin's brothers Vili and Ve, also known as Lodur and Hoenir, founded the Vanir and Alfar (elf) clans. Unfortunately, the surviving evidence is too scant to definitively determine which was which.
To complicate the matter, we sometimes find the jötun Loki, identified as Odin's brother in scholarly writing. It should be noted that in the existing source material that Odin's brother Lodur (Vili) is a biological son of his parents Borr and Bestla, whereas Loki is not. By all accounts, Loki is said to be of giant-birth, the son of the giants Farbauti and Laufey or Nál. Lokasenna 9, however, informs us that Odin and Loki had become blood-brothers:
"Do you recall, Óðinn,
when we two in the old days
blended our blood together?
you told me you would not,
unless it was brought to us both?"
—Ursula Dronke translation (1997)
The blood-brother ritual involves walking together beneath a raised piece of turf, mixing blood into the earth beneath the strip, and swearing an oath of fidelity. Fóstbræðra saga, ch. 2 describes the ritual in this manner:
"It had been a tradition among men of renown to become bound to each other by a law which stated that whoever outlived the other would undertake to avenge his death. They had to walk underneath a triple arch of raised turf, and this signified their oath. The arch was made by scoring out three lengths of turf and leaving them attached to the ground at both ends, then raising them to a height whereby it was possible to walk underneath them." Martin S. Regal translation (1997)
Gísli Saga, ch. 6, adds additional details:
"Then they propped up the arch of raised turf with a damascened spear so long-shafted that a man could stretch out his arms and touch the rivets. [After walking under it] …they drew blood and let it drip down onto the soil beneath the turf strip and stirred it together—the soil and the blood. Then they fell to their knees and swore an oath that each would avenge the other as if they were brothers, and they called on all the gods as their witnesses."
—Martin S. Regal translation (1997)
As we have seen in Gylfaginning and in Völuspá, Odin is sometimes accompanied by his biological brothers Lodur and Hoenir, also known as Vili and Ve. They take part with him in the slaying of Ymir, the creation of the heaven and earth, and in the creation of man. However, in some sources, Loki replaces Lodur in the triad, such as in the poem Haustlöng, when Loki accompanies Odin and Hoenir to Thrymheim, the home of the giant Thjazi, and in Skáldskaparmál, when the same trio pays a visit to the dwarf Andvari. I would suggest that Loki's special status as Odin's blood-brother allows him to functionally assume the position of Odin's actual brother, Lodur-Vili, and thus, on occassion, also appear as Odin's traveling companion, alongside Odin's own brother Hoenir-Ve.
Excerpt from http://www.germanicmythology.com/original/HeimdallBridgingtheGap.html
-Research by William P Reeves