What?

The dating site that I chose was Match.com.  I chose it because of the amount of traffic it has, and the variety of people on the site. 
Well, someone else that I know apparently chose it for the same reasons. 
I received a text in the middle of the night asking if this was still my number.  I answered yes, that it in fact was, and who was the person contacting me? 
The answer that I received startled me.  It was my sister's ex-husband, telling me that he had come across my profile on Match, and that he was surprised when they assigned an 80% match between the two of us, and what did I think of that? 
I replied something along the lines of, hmm, odd, well good luck. 

He then asked my sister about it, about my single status. 
What? 
Basic rule guys, if you date, marry, and father children with one sister, the other one is off limits.  She IS NOT interested in you.  AT ALL, no matter if you are both single or not.  NO.  Go away.