Doctor Who: 10 Characters Who Should Return For Russell T Davies New Series
5. Luke Smith
Luke Smith was Sarah Jane's adopted son. He began his life as The Archetype, created by The Bane in order to help them with their plan to gain control of humanity through their Bubble Shock drink.
After being saved from The Bane, Luke lived with Sarah Jane and learned how to live a normal human life. Luke met the Doctor and their friends when the Daleks and Davros tried to destroy reality itself in The Stolen Earth and Journey's End.
Luke was later saved by the Doctor while crossing the road, and not paying attention to the car that could have hit him. Eventually, he left the Bannerman Road gang to go to university in Oxford but stayed in contact with everyone. While he was away, he met Sanjay. Sarah Jane pointed out that Sanjay was looking at him in "that way" and said he should go and talk to him.
Luke and Sanjay became close and eventually married. What we don't know is whether Luke told Sanjay about his secret history, and all the adventures he had while saving the world. It could be interesting to see the impact it would have on the relationship if the truth came out.