He does. But given that this is a family show, it has never gone beyond implying. However it is known that the Doctor has "danced" with, as an example, River Song (implied in several episodes, most notably "The Impossible Astronaut"). The term "dancing" was introduced as a direct metaphor for sex in the Steven Moffat episodes "The Empty Child"/"The Doctor Dances" and reiterated in "The Girl in the Fireplace" (another episode where sexual activity for the Doctor is strongly implied, in this case with noted courtesan Madame de Pompadour). Also, the existence of a granddaughter, Susan, indicates the existence of a male or female offspring of the Doctor's at some point. In addition, although it does not really happen in "The Family of Blood" the Doctor, having just come out of his John Smith human persona, imagines having children with Joan Redfern.