Doctor Who: 10 Things We Actually Know About The Doctor's Family

In The Empty Child, Doctor Constantine says that he was a father and a grandfather and now he is neither, something that the Ninth Doctor relates to. The first Russell T Davies era contains several similar references to the Doctor's children, the most notable of which comes in The Doctor's Daughter.

Struggling to understand the Doctor's reluctance to accept Jenny as his own flesh and blood, Donna has a go at him, only to discover that his new 'daughter' is an unwelcome reminder of the children that he lost.

This is never elaborated upon and we don't know exactly what happened to the Doctor's children, whether they were killed during the Time War, or at some undisclosed point before he took custody of Susan – although the Tenth Doctor does explicitly state that they died, so as far as he's aware at least, they aren't still out there to be found.

Interestingly, William Hartnell once pitched a Doctor Who story in which the First Doctor would encounter his evil son (also played by Hartnell), which, had it gone ahead, may have ended up shedding light on the difficult questions surrounding the Doctor's kids.