| Simplistically stated; however, some people don't know who their real father is, even though they think they do Decades ago it was shameful to have a child out of wedlock, and a mom would marry someone who was not the real baby's father. If you do know who your real father/mother is ... ask them if they recall a serious flu ... Or how many episodes of flu they recall. Did dad serve in a war? Did he have a personality change, horrible headaches, short term memory loss? Does diabetes appear to run in the family? That might most probably mean a chemical exposure that causes diabetes 'runs in the family' | 
