House of Húrin
The House of Húrin were the descendants of Húrin of Emyn Arnen, the Steward to King Minardil of Gondor. Húrin and his House were noted as being of high Númenórean blood, but they were not members of the Royal House of Gondor itself.
After Húrin's time it became traditional for the Steward to be chosen from among his descendants, and ultimately the post became hereditary. After the loss of Gondor's last King, Eärnur, the Stewards of the House of Húrin took up the rule of the South-kingdom. Denethor, Boromir and Faramir were all descended from this House.