1. Elrond was born in Arvernien, in the First Age, to Eärendil and Elwing. Being descended simultaneously from the First and the Secondborn, Elrond and his brother Elros were known as the Peredhil (the Half-Elven). In their ancestry can be found the two marriages between Elf and Mortal that took place in the early History (Beren and Lúthien, and Tuor and Idril). The third such marriage would take place between Arwen - daughter of Elrond - and Aragorn - distant descendent of Elros.
"And in the glory and beauty of the Elves, and in their fate, full share had the offspring of elf and mortal, Eärendil, and Elwing, and Elrond their child." [S]
Please Note that "Half-Elven" is a simplification of the brothers' heritage. In truth, they are: 1/16 Maia, 6/16 Mortal, 9/16 Eldar. If you would like to see The Peredhel Math please click here.
2. When Eärendil was away at Sea, the sons of Fëanor (searching for the Silmaril) attacked the exiles of Gondolin who dwelt in Arvernien. Elwing, to save the jewel, cast herself into the Sea, carrying it. Elrond and Elros were left on their own and, thus, were captured by the assaulters. Maglor (the second of Fëanor's sons) pitied the children and spared their lives, leaving them to fend for themselves at the entrance to a cave.
"Great was the sorrow of Eärendil and Elwing for the ruin of the havens of Sirion, and the captivity of their sons, and they feared that they would be slain; but it was not so. For Maglor took pity upon Elros and Elrond, and he cherished them, and love grew after between them. " [S]
"The infants were not slain, but left like 'babes in the wood', in a cave with a fall of water over the entrance. There they were found: Elrond within the cave, and Elros dabbling in the water." [Letters]
On the name "Elrond":
From this background story came one of the interpretations of Elrond's name. "El-" referring to Elf and "-Rondo" to Cavern (in this context, the Cave where he was found) - thus: Elf of the Cave.
Another interpretation takes "El-" to mean Star and "-Rondo" refers to any domed structure (not merely a cavern) - the dome of the firmament. Thus, literally, Star Dome. Which is also occasionally presented as Vault of Heaven. (see "Letters".)
3. Elwing was saved by Ulmo, and sailed with Eärendil to the Blessed Realm.
4. The Valar decreed that the Half-Elven must choose their fate. Elrond, like his parents, chose elvenkind. And he received all the power and wisdom of the Elves. But Elros opted to be counted among Men, and was granted the gift of Mortality.
"Wise in all lore is Master Elrond." [Sauron, The Silmarillion]
"Would that Elrond were here, for he is the eldest of all our race, and has the greater power." [Aragorn, RotK]
"A great power." [JRR Tolkien, Letters]
5. By the end of the First Age, Elrond dwelt in Lindon with Gil-galad, High King of the Noldor, who would influence his life through most of the Second Age.
Please Note:
* Characters placed on the left side of a horizontal line are Male, characters on the right, female.
* If Elrond is the unit (16/16), then characters on:
* Eärendil's line are each 8/16 (parents)
* Tuor's line are each 4/16 (grandparents)
* Huor's line are each 2/16 (great-grandparents)
* Galdor's line are each 1/16 (great-great-grandparents)
Therefore, they descended from:
1. The Three Houses of the Edain (6/16)
House of Bëor - Beren (2/16) and Rían (2/16) - 4/16
House of Hador - Galdor (1/16)
House of Haleth - Hareth (1/16)
2. The Eldar (9/16)
King Thingol (Elwë) (1/16) and Nimloth (4/16) were Sindar - 5/16
Idril was the daughter of Turgon, King of Gondolin, High King of the Noldor - 4/16
3. The Maiar (1/16)
Melian (1/16)
In short: 1/16 Maia, 6/16 Mortal, 9/16 Eldar
