The Slaughterhouse Siblings

The Slaughterhouse Siblings (unknown – 1868) was British Templars, operating out of London during the nineteenth century.

The nastiest brother and sister duo in London, Charlie and Big Pete are known as the "Slaughterhouse Siblings." The siblings are from a Templar family dating back decades. Hired to punish those in debt to the Templar Order, they often leave their victims lying gutted, their innards replaced with those of exotic animals.  Henry Green provided the Assassins Jacob and Evie Frye with the siblings' name and location, finding them in a pub of the City of London borough – where they make Charlie kill her brother.

Reference

Assassin's Creed: Syndicate