[Ivriniel]

In the Tale of Aragorn and Arwen, there is a particular reference made to Elrond's children--beyond Arwen--as the Sons of the Half Elven. Elrond, I think himself, states that there is a requirement that his children actually be with him for their journey in the West, in order for them to have the Life of the Eldar.

Elladan and Elrohir did not take the Western Road with their father, and I understand that to mean that they made the choice to live a mortal life. They died in Middle Earth, and they had close ties to the Rangers of the North. I suspect they took wives who were of the Dunedain and fortified the longevity of the Numenereans in Exile in the Fourth Age.

Dior, as I remember, was also not someone who had the life of the Eldar. Luthien chose a mortal life, which is a slight variation on the way the mythology puts the Choice of the Peredhil (Half Elven). Dior being Luthien's and Beren's son cannot claim an immortal life in that context. However, I also recall that Luthien's end was prior to the War of Wrath at the end of the first age. The Choice of the Peredhil was put together by the Valar, formerly, after Earendil in Vingilot made it into the Uttermost West and pleaded with the Valar to render aid. Earendil's plea was successful, but something else came of it, which was his immortality, which to that point, had no precedent (again, Luthien perished, having relinquished her heritage, somehow). I also seem to remember that Earendil was actually somewhat reluctant to take on the Life of the Eldar, but did so for Elwing's sake and by her plea to her husband. He certainly has a very boring life, I would say, rising day after day, in Vingilot, as the Evenstar, and as he must until the fulfilment of the Second Prophesy when Melkor returns through the Doors of Night. I'm not sure I would want to live that way!

Cheers
Ivriniel