Karan, hes always loved Nandini especially after that 3yr leap when she came out of coma, he rushed off to the hospital to see her not giving the fact that hes married to Tanya a second thought.
I won't say he didn't love Tanya, but she was his second love, i think he had that feeling coz she was his best friend. But the whole time, hes only ever truly loved Nandini.
Shaheen