Gabriel Tyler
Gabriel Tyler was Jacob and Winnie Tyler's son, and the twin brother of Steven Jericho. His father abandoned the family in June 1977, even though he knew Winnie was pregnant.
He and his brother were born several months later. Needing money, Winnie decided to sell one of the twins to the Jerichos. The four-year old Bev secretly followed and saw the transaction, which took place on Christmas Eve 1977. However, Winnie was so ashamed of what she had done that she never spent the money, staying in the Quadrant and raising Bev and the twin she kept, Gabriel.
Gabriel had a low-level Glamour, making people view him favorably. He also was mildly telepathic. The twins were psychically linked, and their separation damaged the connection. This caused Gabriel to unknowingly drain energy from Steven.
After ten years, Eva Jericho brought the sickly Steven to Winnie, asking her to exchange the "damaged goods" for a healthy son. The proximity of his twin caused Gabriel to draw the remaining life from Steven, killing him. This vampiric event activated the N-Form that had been searching for what it thought was a vampire infestation on Earth. It merged with Eva and Gabriel, then went on a killing spree in the Quadrant. The Seventh Doctor was finally able to deactivate the N-Form by causing Eva's death, which also killed Gabriel. (PROSE: Damaged Goods, AUDIO: Damaged Goods)