This topic may seem taboo, but ask any family therapist and you'll learn that they've been approached about this subject for years. When therapists bring it up, people think they're crazy until it happens to their family.
Sexuality between step-siblings is rare, but it does happen. In nature, biological siblings are repulsed by the concept of sexual feelings towards each other. There is something about having "shared DNA" that is a very strong deterrent when it comes to sexual attraction, and it's also one of the reasons that incest is so rare among biological siblings.
If you were to ask a man or a woman if they've ever had sexual thoughts about their biological sibling, you'll immediately hear something to the effect of, "No, that's disgusting!" even if their sibling is a very attractive person.
On the other hand, stepsiblings do not share the same DNA, so they are not repulsed by each other like biological siblings are naturally. Still, society tends to frown upon stepsibling relationships. While society's views on stepsibling sexuality closes the door on intimate relationships, it does not lock it.
Is there a law against stepsibling marriages?
If you wanted to marry your stepbrother or stepsister, there is nothing in U.S. law that says you cannot do it. There is no U.S. law that makes it illegal for stepsiblings to become lawful husbands and wives.
Even though you may be related through your parents' marriage, you are not related by blood, therefore, you are not subject to consanguinity laws, which make it illegal for close blood relatives to get married. Consanguinity laws make it a crime for the following relatives to get married:
- Biological brothers and sisters,
- Aunts and nephews,
- Uncles and nieces, and
- Many states say it's illegal for first cousins to marry, however, all states say that second cousins are allowed to get married to each other.
Since stepsiblings are not blood relatives, they are legally free to marry each other. There are no state laws that prohibit marriage between stepsiblings since they are not at risk of having children with genetic defects due to being close blood relatives.
If you have further questions about your state's marriage laws, please contact a family law attorney!