((Copied from the Encyclopaedia of Arda. Don't think they'll mind. I will try not to stray too much from cannon, but sometimes interpretation might be necessary))
One of the greatest Elves in the history of Middle-earth, Elrond was born at the Havens of Sirion late in the First Age. During their sack, he and his brother Elros were taken captive by the Sons of Fëanor, but Maglor took pity on them and released them. When they were rescued, Elrond was found playing in a cave beneath a waterfall, and so received his name. ((roughly, elf-of-the-cave))
Both of Elrond's parents were half-elven, and after the War of Wrath he was given a choice; whether to be counted amongst the kindred of Elves or of Men. He chose the Firstborn, and remained in Lindon with High King Gil-galad.
After the invasion of Eriador by Sauron in the mid-Second Age, Elrond founded a refuge there in a deep hidden valley; this was named Imladris, or Rivendell in the Common Speech. After Sauron's defeat by Tar-Minastir of Númenor, Elrond remained in Rivendell, where he prospered with the aid of the Great Ring, Vilya.
Elrond played a great part in the histories of the Second and Third Ages; he marched with Gil-galad and Elendil to the War of the Last Alliance, and was a leading member of the White Council. At the time of the Council of Elrond in 3018 (Third Age), he had dwelt in Middle-earth for some 6,500 years.
Elrond is a lore master and a healer, a man of leadership but also a quiet and loving friend. Many hardships built a deep sense of compassion. He is very fond of the descendants of his brother Elros, for not only he restrained from throwing the One ring with Isildur and all when his kin refused to throw The One in the fires of Mount doom; but also he is the keeper of the heirlooms of the royal line and also the major benefactor of that line. When Arathorn untimely lost his life, the wise Gilraen knew whom she ought to look up for aid.
Elrond fostered Aragorn and loved him as one of his own, even giving him another name for the lord was afraid the disclosing of the heir's identity would be his ruin. those few first years of peace were a much cherished interlude from the struggling he was used to, as a ruler and enemy of the One Enemy. Upon his adulthood Elrond revealed to him his line and name. When his daughter Arwen returned from a regular trip to her grandparents Galadriel and Celeborn in the Golden Woods, Aragorn had instantly fallen in love for her.
Aragorn had been heartbroken, and Elrond much grieved to see him so, but the Evenstar was much beyond him. It was the lad's first infatuation, after all. Aragorn bid him goodbye and begun his long opposition against Sauron, growing in spirit and in body, equal even to his sons, and Elrond was very proud of him. But one day, Aragorn and Arwen met at cerim Amroth, and later Elrond was told they had plight their troth.
One way or another, Elrond had much to loose. Foresight is not an advantage by default, for it also makes one suffer in anticipation for things he cannot always change. Either the line of men would have his nobility restored, Gondor would regain their King, the enemy would be defeated and he would loose his beloved daughter; or Aragorn would fall and perish in the combat like so many before him, the world would plunge into shadow and all the things they loved in Middle-earth would be lost. Arwen would sail across the sea, leaving her heart behind- for he would not let her be the bride of anything less than a king.
Thus the long hard fight against darkness has a bittersweet taste for the lord of Imladris, Elrond Peredhel, son of Eärendil, herald of Gil-Galad. And yet, there is only one path for him, truly.