I have the similar problem as you had. Could you tell us if you finally found the problem?
Hi,
The blood may come from anywhere along the passages of air. The first to consider is the nose, if there is any blood whenever you clean the nose. The second is the mouth, as you may be swallowing some blood (you may be able to detect some blood when you brush your teeth, a visit to the dentist would be best). Is there any pain in your mouth when you wake up? If you are breathing through an open mouth when you sleep and the air is dry, the drying effect may injure your mouth/throat, so a little blood may come. It would also be best to see your doctor to get a thorough examination. Your concerns are valid, even some people who do not smoke get lung cancer. The impact of a family member having one, may not really increase your risk for cancer (unless there are also a number of different other cancers in the family). Stay positive.