Asad and Ayaan maybe not blood brothers.

I dont think Asad and Ayaan are blood brothers and maybe Ayaan is Shrieen first husband's child

Rashid married Dilshaad had Asad

Shrieen was earlier married and had Ayaan and Nikhaat (the rishta wali girl) with her first husband but he died i think

Shrieen fell in love with Rashid and had Nuzhaat (the glasses and braces girl) with him and they got married but kept it a secret

Rashid and Dilshaad had Nagma around the same time and that's why Nuzhaat and Nagma are the same age and in the same college

Shrieen's brother found out and with money he blackmailed Rashid to leave Dilshaad altogether and his 2 children and Rashid being the greedy person that he is disowned his first wife and children for money

So Rashid has 3 children of its own and he adopted 2 of Shrieen's children.

The tagline lady with her husband has 2 girls. I think one of them is married and the other one is Humeria.

Thats how i think it happened because dadi was saying to Ayaan that Rashid got married to your mother to give you support or something along

and for the future story-line i think this will happen

Ayaan will fell in love with Zoya then divorce her and she will get married to Asad and will fell in love with him and Ayaan will marry Humeria as the tagline lady wished