Are you talking about the husband or the son? 
( Just me being snarky)
When my wife and I decide on a course of action with our son, who by the way is an absolute, heaven sent, angel, we talk over what we are going to do and reach and agreement. All this is before our son hears word one from us on the subject. This way he can’t play one of us off on the other, look for support from the other and so forth.
Hope this helps
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