It's a matter of perception wether ankita looks older. To me she looked older because of archana and I was totally worried whether she would be able to pull the two roles off but she did and I certainly can distinguish between ankita and archana, in fact in the episode where she has her bridal wear on and soham gives her a kiss on the forehead, ankita looked really young in there. So it also depends on the type of makeup one has on.
As for Rushali, it's assumed she is much younger than archana.
Age really doesn't matter when it comes to pregnancy. One can have a child in their forties.
So for example: Purvi has Pari and Ovi has Pia. But Teju has no child, if she marries now, she could quite possibly be having a child aged 40+. Pari and Pia are already 20+. So there would be a gap of 20+ years between cousins. If Pari was to bear a child now, Purvi could become a grandmother and Teju would still be just a mother, and remember Teju is slightly older than Purvi as Purvi is the younger sibling. Teju would then be a grandmother in 20+ years or if her child is anything like her then 40+ years! By which time Pari's child could bear a child and Purvi could become a great grandma!
Edited by ambolove - 11 years ago