Some states allow first cousins to marry.  Some of those states allow it with restrictions and some have none.  A Spanish speaking couple I knew had asked me to help them learn what they needed for a civil ceremony in Denver back in the 1980s.  So I checked into the process for them and found out all this other information about marriage laws in Colorado.  I always found it funny about the cousins getting married and just tucked it away in the back of my mind.