Answer:
No, Katherine Hepburn and Audrey Hepburn were NOT related. This is a very common question. Although they were both great actresses at around the same era, and share the same last name, they are NOT relatives. In fact, Givenchy (a fashion/costume designer and Audrey Hepburn's close friend) was told that he was meeting "Hepburn" for one of Audrey's movies. However, when he found that it was Audrey and not Katherine, he started to leave. See...even HE got mixed up. Later, Audrey and Givenchy developed a steady friendship.