2013 ORS § 106.020¹
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 wife or husband living at the time of such 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. [Amended by 1989 c.647 §1]