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Suppose Bob and Alice marry, have a daughter Eve, and some years later Alice dies.

Suppose Chris and Diana marry, have a son Frank, and some years later Chris dies.

Now, suppose Bob and Diana marry -- that would make Eve and Frank step siblings with no shared biological heritage.

Does the Bible, in this case, prohibit Eve and Frank's marriage? In particular, this question drives at: the prohibition of marriage between siblings -- is it due to genetic or emotional reasons?

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2 Answers 2

The prohibited forms of incest are found in Leviticus 18.

Verse 9 is of the most concern:

9 “‘Do not have sexual relations with your sister, either your father’s daughter or your mother’s daughter, whether she was born in the same home or elsewhere.

Verse 11, however is also interesting:

11 “‘Do not have sexual relations with the daughter of your father’s wife, born to your father; she is your sister.

Here, only children born of the father are considered. As such, a step sibling sired by another man (such as the case you posit) would appear to be fair game.

The complete list disallows:

  • your mother
  • any woman your father marries (honor)
  • your sister, or the daughters of either of your parents
  • your children's daughters (honor)
  • your father's wife
  • your aunt on either side (she is "a close relative")
  • your daughter-in-law
  • your sister-in-law

In many cases, the point seems to be "don't dishonor your family." I suspect (and here I put on my Rabbi hat and accent), the idea would be that you could not seek out your step-siblings, but if the marriage were to occur before your father and her mother were to marry, that they would be dishonoring you, not you them.

All of this, of course, is far more legal and lawerly than Christianity normally gets, but you asks the question, you gets the answer...

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The Bible doesn't specifically address this. Unfortunately, The Bible isn't clear on the reason for not marrying your sister, and the idea of non-blood relations isn't addressed. There's actually a chart on Wikipedia matching verses to types if potential incest, and for step siblings, there's nothing.

This is not to say it's O.K. or not. There are plenty of specifics the Bible does not address specifically.

  • It does not specifically mention masturbation.
  • It does not mention whether or not it's O.K. to buy your wife flowers.

When there is no clear Biblical statement in a moral issue, such things are next determined based on extrapolating Biblical principles.

For the first item in my list, for example, Jesus said if you look at a woman to lust after her, you've committed adultery in your heart. By extrapolating, if you're doing that, you're probably lusting after something, so it is wrong.

For the second, there's no Biblical principle condemning it, so there's no problem.

So the answer to your question remains "there's nothing specifically forbidding it, and genetic similarity isn't cited as the reason for the prohibition on sexual relationships with close relatives." I still don't know if that makes it o.k., though.

Perhaps a better follow-up question that may have more definitive answers, you could ask what is the Catholic view on this, or another denomination...

Next, in some places, marrying a step-sibling is illegal, so the admonition to obey secular authority would apply.

The final test is the test of conscience (which can be seared, so the lack of conviction from your conscience can be deceiving).

The following is my personal take, not a doctrinal take. For what it's worth...:

I have a vague feeling that it's wrong, and most of the time when I have this feeling, and I'm thinking of questions like this, it's like I know it's wrong but am looking for a loophole to get away with it. Once I realize that, I trust my conscience, even though I really want what my conscience tells me is wrong. God gave me a conscience for just this reason.

I can think of dozens of reasons it's a bad idea. What if you break up? How would that affect the parent's relationship? And if you grew up together, it's more than just a little bit more icky. But I'm not sure that's on-topic for this question.

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@DavidStratton I think your personal thoughts are a valid answer in itself. It's certainly a bad idea and very creepy. –  Monika Michael Sep 8 '12 at 14:41
@MonikaMichael - Thanks. However, in this case I think Dan is right to point this out. The question isn't "Is it right or wrong" but rather "Does the Bible state it?", and within the question a specific question about whether it's based on genetic reasons. The rest of my answer may be doctrinally correct, but Dan is right that the first paragraph is the only part of the answer that addresses this specific question. I included it only because the question seems to be a springboard to the "Special Pleading" logical fallacy. nizkor.org/features/fallacies/special-pleading.html –  David Sep 9 '12 at 16:27
Great answer. I can't edit for just one char but you may want to fix: "buy you[r] wife flowers." –  Jack Douglas Aug 30 '13 at 12:10

protected by wax eagle Aug 30 '13 at 11:01

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