I think firstly, this man should have been truthful to you bout his failed marriage right from the start. He could have been lying for all you know. Anyway, if you are a person he's sincerely pursuing after, you ought to know it and be given the choice of if you still want to accept him or not. I have come across men who did the same thing to me before, despite having a loving wife and kid, lie that they were divorced, not living together, acting pitiful, I got a great shock upon learning the truth. It's sick how some men can lie their way through just to get some cheap thrill outside their marriage.
I would clearly stay away from such men if I were you. You mentioned he was just wooing you, if you have not fallen for him, i would suggest save yourself alot of trouble and pain in the future, back off and open out to better men out there.
About telling the wife portion, in my case, luckily I had not fallen for him but I could not tolerate the irritation of him lying to me so broke it to the wife, also so that she could be aware of his cheating stints, yet, she could just say he had always been like this, Im not the first one telling her so and she doesnt mind so long as he comes back to her. I was like, WTF!
Anyway, forget bout those losers, back to your case, glad you found out earlier.. move far away from him. If he was truthful after all, he should have revealed it to you way before you found out yourself. If you never happened to chance upon that website, how long was he thinking of keeping it from you? Risky one you are with here.. Beware, take care..