Nienor (First Age 473 – 499, aged 26 years), also called Níniel ("Tear-Maiden"), was Húrin and Morwen's third child and the sister of Túrin Turambar. Her father was a great foe of Morgoth and was cursed by the Dark Lord. That curse would also ensnare his children, leading to the greatest tragedies of the First Age.
She was born in Hithlum in the year of the Nirnaeth Arnoediad ("The Battle of Unnumbered Tears"), during which her father was captured by the servants of Morgoth. After the battle, the Easterlings settled in the land and oppressed the People of Hador. Fearing for her son's life, Morwen sent Túrin to the kingdom of Doriath for safety. As a result, Túrin never saw his sister.
Nienor remained in Hithlum with her mother for twenty years before they went to Doriath in hopes of finding Túrin. He had left the kingdom, but Nienor and her mother heard a rumor that the mysterious Mormegil, war chief of the Kingdom of Nargothrond, was actually Túrin. The two then journeyed out with a company of Elves. Unfortunately, the Dragon Glaurung had just sacked the Elven city, and, sensing their approach, caused a cloud of foul vapor to rise from the river Narog. The party's horses panicked and Nienor was separated, at which point the worm Glaurung used his enchantments to put her in a state of total amnesia.
Eventually, the amnesiac woman was found by Mablung, who intended to take her back to Doriath but they were attacked by Orcs while attempting to cross the river Taeglin. In confusion and terror, Nienor tore off her clothes and ran naked through the forest until she fainted.
Here her brother Túrin found her, naked and terrified, at the grave of Finduilas, the elf-maid whom he had loved. Because Nienor did not remember her identity and Túrin did not know he had a living sister, he named her Níniel ("Tear-Maiden") and brought her to safety in the Forest of Brethil.
The men of Brethil returned to the settlement of Ephel Brandir soon after. When "Níniel" fell sick, Brandir tended to her, secretly falling in love. However, "Níniel" loved Túrin more, and after three years, they were wed. By the next spring, she was halfway through her first pregnancy.
It was then that rumors of Glaurung's approach reached Túrin, who went out to slay him. Unfortunately, the dragon envenomated him even as he dealt the worm a mortal blow, and Túrin fell into a swoon. At this moment, "Níniel", who feared for her husband's life, arrived and found him apparently dead. The dying Glaurung then removed Nienor's amnesia with his last words. Realising she had married her own brother and was carrying his unborn child, she committed suicide by throwing herself into the gorge of Cabed-en-Aras. When Túrin finally awoke, he was told of Nienor's fate by Brandir, but he refused to believe it, and slew him in anger. Then Mablung of Doriath arrived and corroborated Brandir's tale. In utter misery, Túrin killed himself on his sword Gurthang.
The tragedy of Túrin and Nienor's love and suicide ap pear to have been carefully scripted by the curse of Morgoth, as meted out by his servant Glaurung — this was his most dangerous weapon and the coincidences are too great to be accidental. That Nienor would arrive naked and amnesiac on the grave of Túrin's love, who had been tragically murdered; the repercussions of this incident are too specific to not be the work of the curse.
Baragund Galdor = Hareth | | | ______|______ | | | | | | Morwen = Húrin Huor | ______|_______ | | | | Lalaith | | | Túrin = NIENOR