The Family of Blood are a family who appear in the episodes "Human Nature" and "The Family of Blood" (2007) in which they are the titular entity. They are incorporeal, green telepathic creatures and refer to each other by their relationship followed by "of Mine"; "Father/Husband of Mine", "Mother/Wife of Mine", "Son/Brother of Mine" (who appears to assume leadership) and "Sister/Daughter of Mine". Because of their lack of form, they required a physical body to inhabit; they only had short lifespans without them and as such, sought that of a Time Lord and pursued the last Time Lord: the Tenth Doctor, who chose to alter his biodata to become a human schoolteacher in England, 1913 until their lifespans expired; he did this not out of fear but rather as an act of mercy. They had a time vortex manipulator allowing them to time travel. Their spaceship was stolen and was protected by an invisible shield. They could also animate different things for servants — in the case of their 1913 invasion of Earth, scarecrows — using "molecular fringe animation". They also possess hand-held energy firearms capable of disintegrating flesh and cloth - on the Doctor Who official website it is referred to as a "Bio-gun". The Family possessed the forms of four humans: Mr. Clark, a farmer; Jeremy Baines, a school prefect; Lucy Cartwright, a small girl; and Jenny, a maid at the school. The original souls of the humans were replaced, the original bodies only existing as vessels for the Family.
After the destruction of their starship, the Doctor punished the Family for their crimes. "Father of Mine" was tied up in unbreakable chains forged from dwarf star metal, "Mother of Mine" was trapped on the event horizon of a collapsing galaxy, "Son of Mine" was frozen in time and dressed as a Scarecrow, left in the fields to watch over England as its protector, and "Sister of Mine" was trapped inside every mirror and unable to leave, still able to be glimpsed fleetingly by humans. "Son of Mine" mentions that the Doctor visits the sister once every year, and he wishes that the Doctor may forgive her in time