Is it a lie if he "forgets" to tell you?

I have been seeing my new bf for 3 months. I found over the weekend that we have several friends in common. He told me that he is single and never been married. One of our friends let it slip that he is actually divorced. He has no idea that I know this. My understanding is that he was 19ish when he married her and it did not last all that long maybe two years. They have no contact with each other. I am confused that he didn't tell me he was divorced. Its not even that I would have cared. I guess I have doubts about our relationship if you don't feel you can be honest. Should I bring up that I know? Do I let him bring it up?? What if he never brings it up?? Should I see this as a betrayal or no big deal??