Thorin III Stonehelm
Title(s): King under the Mountain; King of Durin’s Folk
Dates: 2866 III - ? IV
Parents: Dáin II
Children: Durin VII
Then Bard II, Brand's son, became King in Dale, and Thorin III Stonehelm, Dáin's son, became King under the Mountain. They sent their ambassadors to the crowning of King Elessar; and their realms remained ever after, as long as they lasted, in friendship with Gondor; and they were under the crown and protection of the King of the West.
-The Tale of Years, Appendix B, Return of the King
Kitt of Lindon 1.30.05