What is the moral of the story here? Don't completely trust any other Bhai-Behen relationship other than real one. It is better to trust friends than Bhai-Behen. In real life as well, I am a witness to such a thing. My neighbor married a guy to whom she used to tie Rakhi earlier.
As this show is for mature audience (as per Disclaimer) (In my opinion, not a family show), we get to learn not to completely trust, if any pair calls themselves brother and sister.