system
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human
[Lord of the Rings] Have there been any cases of a human/elf marriage where the elf continued living long after the human died?

From what I remember reading, the elf always seems to become mortal from the marriage. Or die from being very sad, as elves sometimes do. 

Has there ever been an elf who married a human, outlived them, and didn't become mortal or die of depression? Continued living without being miserable forever?
gpt
It's a little more complicated than that. Each marriage between Elves and Men came with its own set of unique circumstances. 

The first, between Beren and Luthien, ended with Luthien becoming mortal because those were the terms imposed on her if she wanted to get Beren back from death. Beren had died fighting Carcharoth, and Luthien died from grief shortly afterwards. Luthien goes to the Halls of Mandos where she basically makes a plea to get Beren back (Men leave the circles of the world upon death). This is successful, and Beren is returned, but she is now mortal, and they both die about 40 years later. 

The second, between Tuor and Idril, ends with Tuor allegedly remaining a Man, but being granted true immortality by Eru after he and Idril sail west. So in this case, both partners lived on for eternity. Tuor is the only Man to have had this happen. 

The third, between Aragorn and Arwen, ends with Arwen choosing to become mortal. She's one of the half-elven, along with her brothers and father, so she has a choice of which kindred she would rather be with. The act of marrying Aragorn doesn't make her mortal; she could've chosen to be an Elf, but she doesn't want to live without him. When he dies, she gives up her life the following year. 

There's another marriage too - between Imrazor the Numenorean, Prince of Belfalas, and Mithrellas, an elf-maid from Lothlorien. She bears him two sons, and then disappears one night, her fate unknown.

Basically, each Union of Elves and Men came with extraordinary circumstances that affected how each marriage and the fates of those involved ended up playing out. If an Elf was to marry a Man in normal circumstances, it would not make the Elf mortal, nor would it make the Man immortal. If the Man died, the Elf could live on forever, although they would obviously be carrying a lot of grief. Any children from the marriage will be of the race of Men, so mummy or daddy Elf also gets to watch them die too.