what is the reason for Abir and Mishti breakup

So far CVs have been doing a good job . But i don't understand yesterday's episode.What if Kunal is Parul's son. Even if Meenakshi blackmail why didn't Abir question her ' why does he need to break his ties with Mishti '.what connection it has. Am i missing something.

Basically meenu Hates mishti because she's his son's gf and according to itv rules son could not have gfs could not fall in love 

So she blackmailed abir that she'll tell kunal that he's not her son but parul's and he's illegitimate which will shatter kunal of course if he don't leave mishti 

i can understand that but Abir's character so far have not been falling into any trap when it comes to separation between him and Mishti. He didn't bother abt Kunal and he clearly chose Mishti over Kunal but i guess this time it is not Kunal's fault so he decides to let go off Mishti. The main highlight of the story so far has been the lead pair not getting into any misunderstanding or not getting into any sacrificial mode due to any external pressure unlike other TV shows.

i wish the misunderstanding don't get any serious and spoil the story.