You've ever googled where it's legal for first cousins to marry.
Let me save you a little time.
Alaska, Alabama, California, Colorado, Connecticut, Florida, Georgia, Hawaii, Maryland, Massachusetts, New Jersey, New Mexico, New York, Rhode Island, South Carolina, Tennessee, Vermont, Virginia, Washington D.C., and Maine (yes Deb, I am awaiting your comment) provided the happy couple undergoes genetic counceling.
There you have it. May I point out that Oklahoma is not on the list?