Sometimes, a highborn family has the most to fear from within. In the case of the Boltons, bastard Ramsay Snow was the biggest enemy of the rest of the Boltons.
The Boltons were bannermen for House Stark, and fought with Robb Stark for the North against the Lannisters. That is, until the Red Wedding. Sensing an opening, Lord Roose Bolton switched to the Lannister side, helping to assassinate Robb Stark and Catelyn Stark. He became the Lord of Winterfell and Warden of the North.
But a lot has happened since then, with several important Boltons dying along the way. Is there anyone left in House Bolton in Season 7, or has the house gone extinct?
Thanks to the treachery of Ramsay Bolton, formerly known as Ramsay Snow, House Bolton is likely no more.