Re: His mom
We still have no idea what he really says about this to her. Trashing people without reason or just made up assumptions is not a good thing.
Looking for a bahu herself is hardly a strong reason and not to be overcome by the strong position taken by the man. What we know is that this is causing his family difficulties.
Seems 'so far what we know', the man does not feel strong enough for her to persuade or change decision of his mother to approve this relation. Maybe he does, but not known yet.
It takes a good reason in many families where a girl or boy would be able to break a long term relation and love between parents and their children.
Mere few months or perhaps year 'relation without marriage', may not be able to break that relation.
If these signs are there, leave the person alone.