because damini was just karan's first love but nandini is karan's true love have you not seen after damini's marriage with gautam karan forgot her and moved on but he nerver forgot nandini.and abt tanya karan was trying to moved on with tanya but he never moved on with tanya.and plz dont say he has a manthan with tanya because mhir has akaran with mandira that does't mean he loves with mandira.lolz i noe right!!!!!
i mean b4 karan fell in luv wit nandini, he fell in luv wit damini. but nwo damini is gautam. den karan fell in luv wit nandini. dne her had 2 mvoe on n went 2 tanya. dis is so messed up, sometimes it grosses me out at how much ppl can fall in luv.n it hough u can luv only once unless u moved on n fell in luv again.which by da way is rare.