Oh wait. I just had a thought.
Do you think that Shivaay and Tia had agreed on exactly the same contract that he offered the fat parents of the replacement girl???
Were Shivaay and Tia going to get married and then divorced the very next day?
Is THAT fhy the wuck it didn't matter WHO he was getting married to? It's just that he had to get married to someone (khandaani, pila khoon, blah, blah, blah)?
No, that doesn't make sense does it?
But it would explain some things.
Why Shivaay never seemed to care very much for the marriage despite all the noises his brothers and daadi made.
Why Tia's parents were always so horribly business minded about the marriage.
Why till the last minute, Tia husband Robin/Dushyant was persuaded to be quiet and wait.
Maybe this is what Shivaay meant when he was drunk and told drunk Anika that she shouldn't be so nice, because he was bad?
Despite all this, the reason why it doesn't make sense to me is that by doing this he would have been cheating and lying to his family, his brothers! Which doesn't make sense given how much Omkara says he hates lies. Shivaay wouldn't lie to Om. Would he???