[Mithadan]

I agree with Galadriel55 regarding Dior, though this is only an opinion. I do not recall anything written specifically regarding whether Dior would be considered an Elf, a Man, or Half-Elven. In light of this, I might amend my view in my initial post regarding the number of unions between Men and Elves, since Dior wedded Nimloth, an Elf. However, given the uncertainty of the status of Dior specifically, and since the decision of the Valar regarding the Half-Elven did not occur until later, this is merely an inclination.

The "status" of Arwen and her brothers has previously been debated at length here. The Tale of Aragorn and Arwen has Elrond saying that so long as he remains in Middle Earth, Arwen may depart to the West "if she so chooses." This is referred to by Elrond as "the doom that is laid on us." This, while a bit ambiguous, implies that Arwen and her brothers had the choice of Elrond and Elros to choose their fate. Others believe that Elrond's choice was passed on to his children and that Arwen's decision was a form of special dispensation.