user7141: Lord Buddha once said 
"The future humans will have unusual lusts and temptations"
So when i saw a this in a TV series i couldn't define the line,
If two step siblings form a romantic relationship is it against the five precepts?
So what if we say they are independent individuals,What then?

user111: As per the 20 unsuitable women listed, it could break the precept, depending on if one or both are in care of parents/relatives/guardian or if the king/government prohibits such relationships or if it's prohibited by tradition. 
But one should keep in mind that taboo & obviously vulgar behaviors are not discussed under the 3rd precept. That doesn't mean that they don't fall under sexual misconduct. 

7141: <p>Lord Buddha once said </p>

<p>"The future humans will have unusual lusts and temptations"</p>

<p>So when i saw a this in a TV series i couldn't define the line,</p>

<p>If two step siblings form a romantic relationship is it against the five precepts?</p>

<p>So what if we say they are independent individuals,What then?</p>
 111: <p>As per the 20 unsuitable women listed, it could break the precept, depending on if one or both are in care of parents/relatives/guardian or if the king/government prohibits such relationships or if it's prohibited by tradition. </p>

<p>But one should keep in mind that taboo &amp; obviously vulgar behaviors are not discussed under the 3rd precept. That doesn't mean that they don't fall under sexual misconduct. </p>
