I think Kabir and Vansh have a past or may be something connected to that statue Vansh was talking to in the backyard (the girl Vansh was going to marry) and Kabir also mentioned that catching Vansh is his life moreover, so far we don't know anything about Kabir's family.
In the first episode Vansh did call out Neha but she didn't have to go or at-least she could have hided her necklace somewhere safe. As we can see from the conversation between Neha and Vansh, it does sounds like they knew each other from before bcoz he said "cheating me once, is fault of another person but cheating me twice, the fault is mine"
Right now we only know that Vansh is a criminal due to his painful past and i know whatever happened in the past is not an excuse but it will give us a better understanding as to why he is like that? for now i only like his personality ...
Kabir does love Riddhima but right now he is using her bcoz if u really love someone no matter what u won't put their life on the line, specially where the "Risk is higher compared to the Result" instead u will protect them at all cost and i think that is something Riddhima will see in Vansh. Also, as Riddhima mentioned that she grew up in an orphanage and never had anyone close except for Kabir who made her see what love is but i feel may be what she feels about Kabir isn't love and she will realize it later on...