Gray (Adam)

Gray was the brother of Jack Harkness. While the Boeshane Peninsula was being invaded by an unknown alien race, Jack was told to run away with Gray. But Jack accidentally let go of Gray's hand and ran back. Jack never saw Gray again, or so he thought. (TW: Adam)

John Hart mentioned to have found Gray, which shocked Jack. (TW: Kiss Kiss, Bang Bang)

Gray was seen as a hologram. (TW: Fragments)

It was revealed that when Gray was taken by the creatures that attacked the Boeshane Peninsula, he was tortured for several years. Corpses building up around him, he wished that he could join them. Soon everyone was dead and the creatures had left. Captain John Hart managed to have saved him but soon realised Gray had changed. Gray let his hatred of Jack for letting go of his hand consume him. He molecularly bonded a bomb to John's wrist and threatened to detonate it if John didn't cooperate. He made John take Jack back to 27 AD Cardiff where John buried Jack to live forever buried beneath Cardiff.

Gray came to the 21st century and made all the Weevils come out of hiding. He then shot Toshiko Sato which ultimately lead to her death. A banging started from the Vaults which was revealed to be Jack stored in Cryogenics, as he was unearthed in 1901. He told Gray that he'd forgiven him, but Gray refused to listen, so Jack tearfully chloroformed Gray and put him into storage until Jack thinks he would emotionally recover from the horrifying events, which may be never. (TW: Exit Wounds)