ORS 106.020: Prohibited and void marriages.

The following marriages are prohibited; and, if solemnized within this state, are absolutely void:

      (1) When either party thereto had a spouse living at the time of the marriage.

      (2) When the parties thereto are first cousins or any nearer of kin to each other, whether of the whole or half blood, whether by blood or adoption, computing by the rules of the civil law, except that when the parties are first cousins by adoption only, the marriage is not prohibited or void.