Could marriage of two people who share a half sibling but do not share parents constitute incest?
<p>Suppose that two parents have a child named Sam before divorcing. Sam's father then marries another woman and has a daughter, Daisy, while Sam's mother marries another man and has a son, Matthew.</p>

<p>Because Sam shares a parent with each of them, Matthew and Daisy are both his half siblings. However, Matthew and Daisy are not siblings in any way, for they do not share any parents nor do they share stepparents.</p>

<p>Could Matthew and Daisy legally get married and have children if they are living in a state where incest is illegal? Would this count as incest at all?</p>

<p>I would also like to know if there is a term for Matthew and Daisy's relation to each other. (Quarter siblings? Some type of cousin?)</p>

<p>Assuming that neither one of Matthew's parents are blood relatives of either of Daisy's parents, then they do not share a blood relation that would forbid their marriage under any law or standard of incest of which I have heard.</p>

<p>(As for describing the relationship of Matthew and Daisy: The best English term is <em>step-siblings,</em> even though the order of parental relationships that produced them may not be the most common sequence that produces step-siblings.)</p>

<p>Biologically the marriage is absolutely fine. </p>

<p>Legally, you’d have to check the exact laws of the country in question. A country could have laws that are from a biological point of view unreasonable. I wouldn’t be surprised if marriage between adopted children was illegal, for example. </p>

marriage