My parents are related ; What does this mean for my health or my future children?

My grandfathers didn't know they were cousins.So that would mean my parents are like 2nd cousins,right? I'm perfectly healthy as far I'm concerned.No deficiencies socially, academically and physically.So are my brother and sister. In-fact we all do better overall in school then most of the other children.I'm fairly gifted in athletics also and the doctor always comments on my perfect health. What are the possibility of having kids with genetic disorder?Will I suddenly like fall ill and die e_= ? I know it was fairly common before the 20Th century...but still....