Note that what is considered "blood related" varies by state. In about 2/3 First Cousins are considered blood related and in the rest they are not.
In all states incestual marriages are not allow.
In some states sexual acts other than penetration is not considered sexual intercourse and is not considered incest. In Florida "sexual intercourse" is specifically defined as the penetration of the female sex organ by the male sex organ", so oral, anal or gay sex would not be incest. In others masturbation would be incest.
In three states incest between consenting adults is not a crime:
New Jersey: Incest is legal. The top link says participants must be at least 12.
Rhode Island: Incest is legal.
Ohio: Incest is legal EXCEPT with a Parental Figure.
In three states incest can be punished by life in prison (according to the top link):
Idaho
Nevada
Michigan
Note that in Alabama incest is a Class C felony punishable with incarceration of between 1 and 10 years.