Would you tell her?

I've been talking and meeting up with this man for 2 months we've both confessed having feelings for each other, today I found out he lives with his kids mom and she got a photo frame made one of them cute couple ones, I found out because it was a friend who made the frame, they have 2 kids together, his still adamant they're not together even tho this frame was made while we was meeting up and chatting. Would you message and ask her or believe him or just walk away? I don't want to break a family up but all my friends are saying to tell her as she deserves to know.