From the TARDIS Data Core
(A 'Doctor Who' Wiki):
The Family of Blood were green, gaseous predators that could inhabit and control human bodies. Before taking human form, the members of the Family of Blood were kept in small, spherical receptacles. They had very short lifespans, and, if they went without possessing anyone, they would perish in just three months, "like mayflies."
The Family of Blood were in only two episodes of 'Doctor Who' - "Family Of Blood" and "Human Nature". But I believe their species has since returned to present-day Toobworld:
Having gaseous aliens kill the soul-spirit of those bodies' original owners and take them over is the only way I can see to bring a logical splainin to such a disparate "framily".
I don't know why "Tom Frobinson" ended up in the body of a hamster. Maybe that particular "Father Of Mine" was aiming for a guy standing next to the hamster cage at the local pet shop. A case of lousy aim.
The original Heidi must have been French as well as being in synch with the Tooniverse. Somehow she can access a portal into that pen and ink dimension to bring her bluebirds into the flesh and blood world.
Jeff Gordon solidifies the presence of this "Framily of Blood" in Earth Prime-Time (if not 'Doctor Who'), thanks to his League of Themselves appearances in 'The Drew Carey Show', 'Arli$$', and 'Sesame Street'.
Gor-Don may actually still be a human when we first meet him, albeit a very bizarre one. Despite Chuck's objections, "Mom" saw the potential in him to be a host for another Framily member.
I hate the word "framily". Not a big fan of these ads either. Making this theoretical link to 'Doctor Who' is the only thing that makes them bearable to me.....