I told my son that I don't believe his marriage will last.
Is there a reason why you don't think his marriage will last?
I just don't think he and his wife are right for each other.
It's really inappropriate for you to tell your son that you don't think his marriage will last. You should be supportive of your son and his wife, not tell him you don't think they're a good match. If you keep saying those kinds of things your son will probably be really upset with you.
I'm just looking out for my son. I think their marriage is a mistake. What if I told him to split up with his wife?
Its a fine line. If she is a possible danger or cheating on him he should know. But you need to respect his choice and nor have that weird married to my mom type of relationship.