Incest advocates are wishing a New York parent-child couple good luck in their bid to have the practise legalised.
Last week the New York Post reported on the pair, who claim it would "diminish their humanity" if they couldn't tie the knot.
Claiming they should have the right "to the transcendent purposes of marriage" and to "seek fulfilment in its highest meaning", they petitioned the court seeking to overturn the "unconstitutional" rules which make it a felony, punishable by four years in prison.
They have the backing of long-time incest advocates, the Post reported in a follow-up.
Australian man Richard Morris says he's started 130 online petitions in favour of change, without luck.
He said it was the "right thing to do", comparing the current laws to those which used to criminalise homosexuality and interracial marriage.
"We haven't moved any mountains yet," he said, calling it true "marriage equality".
Another supporter is Keith Pullman, the author of a blog called Full Marriage Equality, calling the ban "absurd".
"That same adult can be sent to war, take on six or seven figures of debt, operate heavy machinery, be sentenced to death by a federal court, and consent to sex with five strangers (and marriage with one of them) but can't consent to marry someone they love?"
He told the Post in some cases relatives fall in love without realising they're related, and allegations of grooming are "laughable attempts to deny someone their rights".
Children born of incestuous relationships are more likely to have birth defects, with closely related people more likely to both be carrying recessive genes for congenital defects and genetic diseases. The closer the relationship, the higher the risk.
The anonymous couple - who are said to be unable to procreate - have stayed quiet, their lawyer refusing to respond to requests for comment.