I have absolutely no doubt my dad also has ME/CFS and we both became ill at the exact same time in 1995 after we both received Hepatitis B vaccinations. However I had to tick "An immediate family member has mysterious fatigue but has not been diagnosed with ME/CFS" because he has never been officially diagnosed. I'm 99.9% sure he's not been examined by a doctor who has ever diagnosed anyone with ME/CFS so that's no surprise. By the time he came to accept that he too had it, he was already retired and we were (and are still) living somewhere where he would have to travel much farther than he is willing to go to see a doctor who would be willing and competent to diagnose a sure case of ME/CFS. Thankfully, he sent me (with my mom) some years ago, to fly across the country to see a specialist to examine and diagnose me properly.