Yes. This is a well known fact. Severus Snape has the dark mark. Although, as we all know, as soon as the Dark Lord started to hunt the Potters, Lily in particular, Severus tried everything he could to protect her. He became a double agent, working for The Order Of The Phoenix (Dumbledore) and Lord Voldemort. Voldemort thought Severus was one of his most fateful followers. The Dark Lord thought Severus was a double agent, working ageist the Order. But Severus was working to protect Lily Evans and her only son, Harry.