Ahil worships his mother in a way that anything against her will not be acceptable to him. He considers her to be one who can do no wrong.
Rehaan knows his mother's flaws, tricks and most of all everything that she is capable of.
But, when her evil deeds will be thrown in front of all, Ahil may take the moral stand and once he knows she killed his father and Sanam's entire family, he will not spare her. Ahil, will play the hero, because deep down he is a good man, who knows right from wrong and has a moral stand.
Rehaan, may infact in the future take up for his mother against all odds. He stands by her, however disappointed in her he may be, even today. So, one can see that in the future too, he will stick by her, no matter what. Rehaan, with all his good boy vibes, is still on the wrong side of things. He knows everything his mother is doing, probably even realizes how hollow her assurances to make things right are, and yet he chooses to be silent, and let himself and others suffer for her own goals and dreams. Rehaan has a lopsided moral ground right now. And even his love for Sanam may not turn him against his ammi. This is what might turn him negative eventually. After all blood is thicker than water.
Rehaan while a good guy, knows nothing is black or white. Rehaan understand grey very well, having lived with his ammi and known her plans for long enough. He knows if he doesn't accept grey, his mother would always be wrong to him. Rehaan continues to love his brother's biwi, hoping that at the end of three months, she will be his. He is not even thinking of whether Sanam really loves him back or not.
Rehaan, cannot see beneath Ahil's words, the love his bhai has for Sanam.
I know my post sounds like a Rehaan bashing post, but it's not. Honestly, Rehaan is turning out to be one of the more interesting characters in this show because of all the grey that is in him. He is out and out positive right now, but one also has to remember that he known Tanveers plots and plans and even though it involves hurting him or others, he goes along with them. He does show a lot of anger at his ammi, and rightfully so. I love that he knows where to place the blame and is not misdirected in his anger. Rehaan has a slot of scope for character development and I am excited to see how Ahil and Sanam's closeness will change him. And also how he will react to the more evil kartoots of his mother, like the cruel and psychopathic slaughtering of an entire family. And to placing a life long guild of murder on Ahil's head.
Rehaan, in that sense is more practical and sensible than Ahil. Rehaan knows his mother is wrong on many counts and calls her out on them. She mollycoddles him with fake assurances, but he knows better than to believe them. He suspects every word she utters in assurances.
Ahil, is blinded by the love he has for his ammi. He cannot see through anything she says or does. He couldn't even see through Nida. Ahil is emotional and lets his feelings cloud his judgements. Rehaan is sensible and outweighs everything before coming to conclusions. Like he sees the good man beneath all that Ahil used to be. Even with all the harsh treatment of Sanam, he only encouraged her to see the good side of Ahil.