Just because you and your wife are having problems, does not mean that you go and sleep with different women to "relieve your pain". That is just rubbish and cynical.
Also, as for Ganga, yes, there might have been problems, but it wasn't as if he was being denied from her love or something. Also, Sahil is the major person to take the blame. How dare he betray his love?
As for Mohini, she is good for nothing and she might have just slept with Sahil because she couldn't with Harsh.
As for Harsh, he is handicapped and he understands the situation and also told Mohini that she is sorry for not being able to provide her the status of motherhood.
***** Ganga is at no fault and Sahil/Mohini are to blame only ******