A man and a woman meet online. They enjoy each other so much that they agree to meet, and when they do it is love at first sight. They are so alike it is uncanny and they instantly feel a deep bond, so much so that it is unbearable to separate. They decide to move in together, and shortly afterward they become engaged. All of their friends say the relationship is moving too fast, but they know they were meant to be together.

The state they are in still requires a blood test to check for diseases. They know they are clean, but its’ required anyway. The results come back, and to their shock they are told they cannot marry.
They are brother and sister.

Although this is an unusual situation, it does happen. There is presently a couple in Germany lobbying to get that country’s anti-incest law, Paragraph 173, repealed. Their case has brought the concept of Genetic Sexual Attraction to light - that siblings who are raised separately, or parents who abandon their child at a young age, occasionally develop romantic attachments when they are reunited.

The reaction to this is almost universally “yuck” - incest is one of the last great taboos of Western culture. But should this type of relationship be outlawed? The issue brings into question what “family” means…whether people with blood relations who were raised separately can even still be considered a family. Can two people who have never met really be said to be related? Genetically they are, but our culture focuses heavily on upbringing and living under the same roof. Step-siblings are often family to each other, but they have no genetic relationship. What is family?

There are two primary arguments against incestuous relationships. The first is risk of birth defects in any children - the German couple has four children, two of whom are disabled - due to inbreeding. But let’s suppose a brother and sister in love agree to be sterilized, use an anonymous sperm donor, or adopt a child. If they are prevented from having children together, does their relationship become valid? The other major argument is based on psychological factors: a parent should not have sexual feelings for their child; a brother should not have sexual feelings for his sister. If they do, it is said to be abnormal psychological development - inappropriate categorization of relationships. Assuming that much is true, should it still apply to relatives who have never met before? If there is not already “another” relationship (that of parent or sibling) present, can there safely be a romantic relationship?

Another argument against incestuous relationships is that “God said” they are forbidden. (This often comes from the same people who say that gay marriage will automatically lead to incestuous marriage.) But it’s a false argument, because it again brings into question the nature of family. For one thing, God was pretty vague about blended families, adoption, orphans, and so forth. The religious prohibition is really against marriage between family members and doesn’t take into account the possibility of siblings raised separately or giving up a child for adoption immediately after birth.

So the question remains: should the couple be allowed to get married? If they were getting married somewhere that didn’t require a blood test, could they just keep their mouths shut, as the main character in Jeffery Eugenides’s book Middlesex did? If they promise not to have children with each other, can they get married? Why should they be denied the loving relationship they had prior to discovering they were related? Who are we to say that two consenting adults shouldn’t get married?