This topic is something if one of the characters didn't exist.
Astitva without Simran
Sia and Aastha wouldn't have been born, Abhi would still be a fashion photographer, Neha would've never met Abhi, and Saakshi would still be in the US.
Astitva without Abhi
Simran would lead a happier life, Manas would still be friends with Simran, and Saurabh wouldn't had a heart attack since Aastha wouldn't be born if Astitva was without Abhi.
The only reason I put that Aastha wouldn't have been born because Simran forced Abhi to marry Neha.