Thingol Feanor

Tuor Feanor II. is the son Fingon, and Nerdanel Feanor making him a member of the House of Feanor.

Fingon Feanor would lead his sons - forgoing the Lordship of the House of Feanor and giving up being Prince of Cothique to his younger borther Finarfin Feanor - in order to travel eastward to Mordor where he fought with the Numenorians in trying to stop Mordor, but they failed and were massacred outside of Tol-Durthang at the Second Battle of Tol-Durthang with Fingon losing two of his children and sending the rest back to Ulthuan with a vow to never return to Mordor.

Vow of Fingon
Following the defeat of the army of Numeron against Mordor during the Second Battle of Tol-Durthang the forces of Numeron would retreat within the fortress itself and Fingon would prepare to do the same but before he did he took his five remaining children to the foothills of Mount Doom, and would have them make the Vow of Fingon. The vow basically drove all of the sons of Fingon to work without end towards the destruction of Sauron, and all of his work, and it would be in this regard that he commanded all of his sons outside of Fingolfin to leave Mordor and return to the lands of the Elves and try to raise support against Sauron.