The Doctor's grandmothers
From Tardis Wiki, the free Doctor Who reference
In their youth, The Doctor, according to their thirteenth incarnation, had seven grandmothers.
Their favourite was Granny Five, who told a young Doctor bedtime stories about the Solitract when he was having trouble sleeping.
Granny Five also claimed that Granny Two was a secret agent for the Zygons. (TV: It Takes You Away)