Kinship relation between Arwen and Arargorn

[BeardofPants]

For filling in holes, I CAN NOT recommend Tolkien's Letters enough. Most of the questions (and puzzlement) I had after reading the Sil and Unfinished Tales, were more or less resolved after reading Letters.

Elda:
The union of Arwen and Aragorn is a re-uniting of the sundered lines of Elros and Elrond.

More than that, it linked up the two half-elven lines (Tuor/Idril & Beren/Luthien.) Makes it very much seem like a breeding program of Eru! (Ennobling the line of men.)