How old are shireen's children??

If rashid left dilshad to marry shireen 17 years ago, then the oldest of shireen's kids would be 16 years old. Ayan being the oldest has passed out of college at this age!!!! Moreover nikhat will be maximum 15 and this is well below the marriagable age.

only possible reason is that rashid was a 2-timer and was married with both at a particular point

He was probably married to both at one point and I think they may have known one another for a while since Ayaan mentions how Asad used to make kheer for him when they were younger when he would get sad or w/e.