Atul is clearly the smartest Rajvansh because he ran away before he could be consumed by Meenu and her meanness.
From Kaushal's dialogues today, it seems like he might be back when it strikes the writers. Ketu bhi kahan dikhti hai aaj kal. She only appears for family functions and family photos.
Regarding Abir's dialogue, the dialogue writer must be new so they are not aware of Atul's existence.