I think its a big mess. If Kesar had not left, they could have sorted his feelings for Gulaal as he grew up. But because they were apart and they separated at such a turn of events where there is a lot of misunderstanding and loose ends, things have gotten complicated. And Kesar was always a gullible delicate soul. He needed proper guidance but he was away from those who could properly guide him in the right path. Now he is a confused soul.
His feelings for Talli have always been platonic and i think it remains so. He has thought of her as nothing other than a best friend. But Gulaal has a different place in his life. She is a person whom he trusted blindly and considered as his own...someone he was possessive over...someone for who's love he felt only he had the rights (its not always a romantic love...children often feel that way about their parents...Oedipus complex etc.). However, he never saw Vasant as an outsider in that relationship. His feelings for Gulaal were an extension of his feelings of adoration and love for his brother. At one point Gulaal and Vasat were one to him. But after Vasant was gone, that equation might have changed. To call it being "in love" is too simplistic a view of human emotions. There are layers of what any human relationship is about, especially a relationship that is so intense and deeply set in your soul. What Gulaal and Kesar have must be seen through a different colored glass than the ones we usually use to watch couples. This is no ordinary duo.