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)
By the time after the Last Great Time War, the Ninth Doctor believed that his entire family had died. (TV: Father's Day, The Empty Child) Similarly, the Thirteenth Doctor would later tell her soon to be companions that her whole family had died. (TV: The Woman Who Fell to Earth)
According to one account of the Doctor's early life, the Doctor was a Loom-born reincarnation of the legendary figure known as the Other, who was originally the son of the Time Lord Andred and the human Leela. (PROSE: Lungbarrow) This would make Leela's mother, Neela, a grandmother of the Doctor. (PROSE: Eye of Heaven)