Nathaniel Chambers

 was the brother of Anthony and Katherine Chambers and friend to Peri Brown. He took to the news of the murder of his father badly, drinking enough to pass out at the wake. He comforted the cyberised Anthony, until the Cyber-Leader ordered Anthony to harm Nate so the Sixth Doctor would do his bidding. His back was broken. Peri comforted him until the ambulance arrived. She told stories of their childhood, such as how they were going to get their names, Nathaniel and Perpugilliam, changed to sound more normal. (BFA: The Reaping)

He was later partially converted into a Cyberman to prolong his life. The Fifth Doctor persuaded him that this was wrong, so he destroyed himself at the same time as he destroyed his sister's evil work. (BFA: The Gathering)