One of my most (unintentionally) popular blog posts of all time is titled, “Could the state prevent gay brothers in an incestuous relationship from marrying? Written in 2012, after Prop 8 but before Windsor, I questioned if under Lawrence, the state had a legitimate interest in banning same-sex incestuous relationships, because the couple lacks the capacity to naturally reproduce, and concerns about any hereditary diseases are nil.

If the Prop 8 opinion means anything, what rational bases could the state proffer to justify a ban on consenting, adult incestuous relationships being recognized as marriage? I suppose the rationale about concern for genetic defects in offspring would be nugatory, as two men cannot naturally procreate. In fact, for the two of them reproduce, I think there would have to be a female involved (presumably, the female would be unrelated). Even there, the 9th Circuit more-or-less separated the notion of getting married from procreation, so reason is out. (So this would not prevent two female sisters from wedding).

Now, in the Arkansas same-sex marriage litigation, just this issue is (somewhat) before the Court.

Via Chris Geidner, the government is citing other limitations on the ability to marry as reasons to justify the ban on same-sex marriage. One in particular is the exact issue I raised two years ago:

The law as currently written does not prohibit same-gender close relative marriages. Can all same-gender relatives now marry? Can an uncle marry a nephew? Can an aunt marry a niece? An underlying rational basis for disallowing marriage by close relatives is that procreation with a near relative has a statistically significant higher probability of producing a child with disabilities. The state has a legitimate governmental interest in the health and well-being of its citizens, and duties with regard to the care of treatment of persons unable to care for themselves. Since same-gender marriages do not have the biological capacity to produce children, do the same rules apply to same-gender marriages?

As I argued, ban on same-sex incest are on much weaker constitutional footing than opposite-sex incest. There was a case from the UK where two male twins, separated at birth, married after an “inevitable attraction.” So it can happen.