1. A long time ago, Elves move to middle earth from a place called Valar. In Valar, things never die. Middle Earth is dangerous, filled with things that make sauron look like the punk next door. Elves decide to try and fix things.
Later, there existed a man and an elf, they fall in love and have two children: Elrond and Elros. Elrond decides to follow the elven path and live for just about forever. Elros decides to become follow the man's path (with the elve's blessing and a lifespan short in elven terms but many times the lifespan of regular guys). Elros moves to Numenor, an island between Valar and Middle Earth. The only catch is they can never set foot on Valar. A descendant of Elros does, and the whole island of Numenor sinks. Elros's descendants move back to middle earth and assume the power over the its peoples that the true elves didn't want.
Enventually Elros's descandants begin breeding with 'lesser' people and the "blood of numenor" declines. Eventually, we get to Aragorn, who yes is Elrond's great times about thirty grand nephew.
On Elrond's side, he decides to marry this elf called, well I don't remember, but the elf's parents are Galadriel and Celeborn ( that's right the lothlorien pair). So Arwen is grandchild of the Galadriel and child of Elrond. And Elrond is Galadriel's son-in-law.
Get it?
By the way, this is the daughter Jean, not the dad Robert.