I just wanted to say in most cases the married man would never leave his wife, so Kunal is telling Ishana and Aditi also knows this and is telling her, but in Lakhil's case it's different. Laajo has been seeing Nikhil with Ishana and even bringing her to the house and his family are supporting their relationship and not supporting her marriage to Nikhil and Nikhil thinks Ishana would have made a better wife than Laajo, she wouldn't embarrass him with his friends and their society. That's the reason why it's different to other marriages. In most cases the married man lies to the wife to see the girlfriend on the side and his family doesn't know about the girlfriend, in that case that married man never leaves their wife and the girlfriend is deluding herself to believe he would.
Here we know Lakhil are the lead couple but Nikhil hasn't realised Laajo is the right girl for him, in fact he is embarrassed of her in public, in another serial I've seen the girl then works on herself to fit in with him, his lifestyle and he also meets her in the middle by changing to accept her, but here Nikhil has Ishana who he thinks is ideal, so lets see how they will manage with each other when Laajo is out of the equation, it should be entertaining.
For Kunal he will be heartbroken initially but he will just have to wait a bit longer, probably Ishana will be with him in the end.