We watch "The Doctor's Daughter" (Series 4, Episode 6) where the Doctor, Donna and third wheel Martha plop themselves in the middle of a Clone War. Whilst there, the Doctor meets his daughter/future-baby-mama-wife (um, ew?), Donna figures out how numbers work and Martha has her own 'Shape of Water' moment. So the Doctor has a daughter. Then could he possibly have a grand-daughter? Nah...that's just silly. Wait...what?