The Unions of Elves and Men

[Mithalwen]

Originally Posted by Mithadan

Tolkien's writings make clear why unions between Men and Elves are rare. Gilraen tells Aragorn simply that "it is not fit that mortal should wed with the Elf-kin." But this is not a matter only of Elves having a higher station than Men, though this is, no doubt, a component of the reasons that the two races rarely marry. More important is the fact that such a marriage could only last several decades and would inevitably end with the Elf not only enduring the aging of the Mannish spouse, but also the parting at death which leaves the Elf alone and bereaved for so long as Arda may last.

And not only would they bereft of their spouse but they would also potentially witness the ageing, decline and death of their own children and further descendents. I have known people who have lost children and their grief is perhaps impossible to grasp from the outside- to see generations pass would surely be unendurable. Perhaps that is why Mithrellas fled.