I have to say, that is a bit odd. But honestly, I agree with T and snodderly - go with your gut. Pray about it.
The thing that stands out the most to me is: 1) he says his mother wants you to be part of the family 2) she didn't call because she didn't know what to say (likely true BTW) and 3) you don't trust him.
It's that last one that stands out the most to me. I don't really care about his mother to be honest. She's a symptom of the issue even if a strong contributor. Your H is the issue. Your lack of trust is the issue.
Leaving the door open is different than running through it headlong. The question is which opportunity is this one?
I'm more in the camp that he should earn your trust first. Although it sounds like he's saying "different" things now about you to his family, is it enough to have a healthy relationship? Or is more needed.
Pray about it. The answers and the questions will come. But don't doubt yourself and don't lose sight of the real issues by being distracted by his family issues. They are not the problem to solve. H and your R is.
Is he ready? Is he even planning to talk about the R? What about you? You are very important in this as well.
AJ
"Our lives begin to end the day we become silent about things that matter" MLK Put the glass down... "Yesterday I was clever so I wanted to change the world Today I am wise, so I am changing myself."