Hatfield, McCoy? Are those from the famous feuding clan?
Yes, the Hatfields and McCoys are just that.
From Wikipedia:
The Hatfield–McCoy feud (1863–1891) involved two families of the West Virginia–Kentucky area along the Tug Fork of the Big Sandy River. The Hatfields of West Virginia were led by William Anderson "Devil Anse" Hatfield while the McCoys of Kentucky were under the leadership of
Randolph "Ole Ran'l" McCoy. Those involved in the feud were descended from Ephraim Hatfield (born c. 1765) and William McCoy (born c. 1750). The feud has entered the American folklore lexicon as a metonym for any bitterly feuding rival parties. More than a century later, the feud has become synonymous with the perils of family honor, justice, and revenge.
William McCoy, the patriarch of the McCoys, was born in Ireland around 1750. The family, led by grandson Randolph "Ole Ran'l" McCoy, lived mostly on the Kentucky side of Tug Fork (a tributary of the Big Sandy River). Of English origin, the Hatfields, led by William Anderson "Devil Anse" Hatfield, son of Ephraim and Nancy (Vance) Hatfield, lived mostly on the West Virginia side. The majority of the Hatfields living in Mingo County (then part of Logan County), West Virginia fought for the Confederacy in the American Civil War; most McCoys, living in Pike County, Kentucky, also fought for the Confederacy; with the exception of Asa Harmon McCoy, who fought for the Union.
The first real violence in the feud was the death of returning Union soldier Asa Harmon McCoy, murdered by a group of ex-Confederate Homeguards called the "Logan Wildcats." Devil Anse Hatfield was a suspect at first, but was later confirmed to have been sick at home at the time of the murder. It was widely believed that his uncle, Jim Vance, a member of the Wildcats, committed the murder.
The Hatfield clan in 1897.
The Hatfields were more affluent than the McCoys and were well-connected politically. Devil Anse Hatfield's timbering operation was a source of wealth for his family, but he employed many non-Hatfields, and even hired McCoy family members Albert McCoy, Lorenzo Dow McCoy, and Selkirk McCoy.