Looking at both them, looks like RK's mom had some majaboori that's why she must have married to Kuku. May be RK's father had some debt or something else. She might have tried to explain this to young RK , but may be he wasn't ready to listen or to believe what she said. But now I think Madhu will come to know that and also she will believe
Radha. Also, RK will realize that somehow , from that he will be changed person. ...that could be turning point in his life and this changed RK will definately made an impact on Madhu , until then don't think she is gonna like him. Just a guess ..looking at the characters.