Spot on with your explanation👏
There are no what if situations here.
Fact is Arvi slept together prior to marriage when they were engaged. Arjun touched purvi. I mean they couldn't wait for the piece of paper from law to give them the A-ok to have sex which is whole another issue but regardless they had sex. Arjun had sexual relations with purvi ... This makes Arjun and ovi incest as others have claimed arvi are incest bc ovi is mating with the man who had sex and has a daughter with who is her sister. Married or not.