Sex, breeding, incest - and marriage?

"The mere word incest triggers strong feelings of revulsion in most people. Therefore, any a priori labeling of a marriage as incestuous tends to preclude objective thought about the permissibility of the particular form of the marriage prohibition a tissue ("at issue", but I am dictating this and thought the AI error was funny). Such revulsion stems largely from the confusion of incest with sexual abuse of children. This confusion is not limited to the general public, but extends to the courts as well. The courts, then, are just as confused as the general public.

When criminal incest statutes are invoked, the overwhelming majority of prosecution's are for sexual intercourse between relatives within the statutory definition of incest, not for attempted marriages between such relatives. In a random sampling of 101 criminal Appellate Court decisions on cases alleging violation of criminal incest laws, all 101 cases involve prosecution's for sexual intercourse. More importantly, in 96 cases in which the ages of the incest participants were revealed, 94 involved in adult defendant in a minor child victim. Finally, 94 cases involved father daughter, father adoptive daughter, or step-father step-daughter sexual relationships.

The societal panic/paranoia about incest, however, stems from inbreeding which becomes irrelevant in father adoptive daughter, or step-father step-daughter sexual relationships. (Mother/son issues follow suit, of course.)
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My point is that an "illegal" incestuous relationship is prohibited socially as well as legally yet does NOT necessarily require it to be a bad thing biologically. I would suggest that, should a PIV encounter arise (no pun intended), some manner of birth control is available to make homozygosity a moot point. Then, it's just a matter of keeping one's mouth shut... "

How about a daughter who wants not just her father´s willy, but her father´s baby, too?

But I´m not sure marriage is appropriate here.
Commitment, sure.
But they are already family, without marriage. She is already his daughter. Any children of hers, whether made by him or anyone else, are already his grandchildren.
He should be committed to continued support of his daughter and grandchildren. But a commitment to continued sexual relationship might be avoided.