The Three Families (also known as The Families) were a powerful organisation descended from three different families who systematically manipulated the human race across the 20th century for their own purposes.
In 1928, Little Italy, men belonging to the families Ablemarch, Costerdane and Frines purchased the immortal known as Jack Harkness, though he later escaped their custody. (TW: Immortal Sins) All reference to the families subsequently disappeared from the face of the Earth. (TW: End of the Road)
In 2011, the Families were responsible for Miracle Day, an event which altered the morphic field of planet Earth so that no human being could die, and also so that Jack Harkness was now mortal. It is believed the Families' descendants could number six million in the present and that they have conspired to manipulate the human race over the entirety of the twentieth century. Is it believed one family took infiltrated politics, another the economic world, and another took over the media. (TW: The Gathering) In the present, the Families had moles in various organisations, including the Central Intelligence Agency. (TW: End of the Road, The Gathering)
Immigrant Angelo Colasanto rescued Jack from the basement in Little Italy shortly after Jack's purchase, but denied knowledge of the three men (TW: Immortal Sins); his granddaughter, Olivia Colasanto revealed in 2011 that the Families refused to work with Angelo because of his homosexual relationship with Harkness, but that Angelo kept a close eye on their activities over the twentieth century. (TW: End of the Road)
The Families were behind the activities of pharmaceutical company PhiCorp, far-right politician Ellis Hartley Monroe, and through PhiCorp also Oswald Danes, a convicted murderer and rapist who commanded a lot of television attention. (TW: Escape to L.A.) PhiCorp COO Stuart Owens however did not even know of the Families existence, and his attempts to research who was manipulating his company were largely fruitless;
The Families discovered the location of (or created) the Blessing in 1998. (TW: The Middle Men, End of the Road. The Blessing was a fleshy tunnel seemingly going straight through the centre of the Earth, connecting Shanghai to Buenos Aires. (TW: The Gathering)