Okay y'all hear me out. I have a feeling his presence is not only to throw off Dev and blow him away and completely destroy his mumma boy attire.
So here is my guess (which could be totally wrong ofc)
1) I think due to lack of money and sheer poverty, Ishwari may have agreed to intimacy with Khatri for money.
2) If not this, then as a lot have already guessed, Dev might be Khatri and Ishwari's son.
Either way, his blindfold envisioning her as a Goddess is wrong because even if the above are untrue, her deeds aren't worth forgiveness. But if they are true, he won't recognize mom anymore.