When Najma was telling the story to Zoya she said Asad was 7 when Rashid brought him to live with Dilshad and family. Ayaan was 2 1/2 and she wasn't born yet. I'm not sure if Najma and Nikhat are around the same age and Nuzhat is the last one.
So in theory (if we round up and assume the math is correct 😆)
Asad could be 25, Ayaan 21, Najma/Nikhat 18 and Nuzhat 16 or 17
And if Zoya was about 3 when the fire happened as it truly was 20 years ago then she should be around 23ish
Does that sound about right?