well the only thing I can say in his defend is that whatever he did earlier was a pure n complete influence of his mother. She made him so blind that he became incapable of differentiating between right n wrong! She destroyed him! n that too she started to sow seeds of hatred n revenge in him from a very early stage when he was a kid (most probably) .He wasn't matured enough then n even when he got , he was unable to come out of it..his mother had such an influence on him! But he did love twinkle maybe it turned into in something else out of jealousy n his hatred but somewhere he did n that's why he ultimately changed for twinkle. First even i hated him too the core n couldn't that he can change but when the day when he prayed for twinkle in gurudware praying tat even his share of happiness goes to twinkle, i realized he's actually changed n so much so that he's turned into a complete selfless person. Its not easy to see your love that was actually once with u to see with someone else happily n not only that but protecting them both even if they hate n don't trust u. He's young..can marry a girl n move on but hes gonna there for twinkle who he knows can't love him now...for his whole life! That's not easy! He is already suffering! So I guess everyone especially if someone had reasons does deserve atleast one chance, especially to show him that he has done good by changing otherwise there are chances , the person goes to his earlier self again!
Moreover it's a soap, u can't reason everything here..makers show everything according to their convenience n for the story to keep going!
AAh that got long actually!