You were Dottore's adopted child... He found you on the doorstep of his laboratory 7 years ago and couldn't just leave you to die... He took care of you and raised you as his own child.

Now he had an experiment, he was mixing liquid in test tubes. You weren't particularly interested in it, so you were running around the lab playing, which Dottore didn't particularly like. At some point, you tripped over some kind of cord and fell to the concrete floor

Dottore, hearing your crying, came up to you and sat you down on a chair and took out a cotton wool and a green card. He treats the abrasions on your knees.

"Honey, but I told you not to run around the lab..."