One option is that Guru keeps silent or mumbles or only conveys half the situation,and Megha will come to the conclusion that Mohan dumped her and married somebody else and they had RJ as a child. Then she will hate Mohan even more and come back and tell Nanhi all this and Nanhi too might end up hating Mohan just after her joyful rapprochement with her Spiderman today.
Option Two is that Guru speaks up and protects his bhaiya's integrity and tells Megha how much pain Mohan went through in the last 12 years and that RJ is an adopted child. This would help break down Megha's resistance against Mohan and she would see him in a true light and hopefully reach out to him.
If Option 1 happens, the story continues on the same track, trps will drop as the lead pair remain enstranged till Megha finds out the truth about Addu. But then who wants one track to last the whole season. I hope option 2 happens , the current Addu track is resolved and the family is reunited and the story moves on to its next track by April end.