These kind of problems, in fact, has increased, these days, because of societal change
Such problems can easily be taken care of by:
1. Consulting a psychiatrist
/ clinical psychologist
2. We need to evaluate whether he is going towards depression
3. Is he going towards a kind of "marriage aversion" or denying to see other girls for marriage etc
These are the some of important issues that will be discussed with the doctor and he will be handled emotionally.
It will take few sessions and things should improve with this.