Lúthien is remembered in the Lay of Leithian (Escape From Bondage). She fell in love with the Man Beren, of the House of Bëor. Their relationship was doomed from the beginning: Lúthien was not only the cherished only daughter of the most powerful king in Beleriand, she was also an immortal elf. Beren, meanwhile was a mortal man on the run from Morgoth, the Dark Lord.
Thingol was desperate not to let Beren marry his daughter, and set an impossible task as the bride-price: Beren had to bring to Thingol one of the Silmarils from Morgoth's iron crown. Against monstrous odds, including kidnap by the sons of Fëanor and the death of Finrod Felagund, as well as a confrontation with Sauron, the couple achieve the task, but Beren dies as soon as it is completed.
Lúthien gives up her immortality to let Beren live again, and they dwell in Ossiriand until after the sack of Menegroth. They have a son, Dior, who is called Elúchil - the Heir of Thingol. Her line will never be broken.
The Line of Lúthien