I didn't bring up MY A but I did bring up his mum's affair.
Cowardly I know, but it was a way for me to bring up the topic. Unfortunately it was towards the end of the session, but at least the topic is in the room now and she said she wants to bring it up next time we meet, i.e. how his mother's affair has affected him and if he ever wonders/worries that his wife will cheat. Yes.. even at that point he said nothing.
I can see at this rate, it really IS up to me to initiate my A. It really is a massive wedge between us and you're all right.. there's a massive elephant in the room and we are skirting around it. We spent the majority of last nights session talking about the details of his brother's messy divorce.
I am really scared of how he will react and that he may leave me, but, if we don't talk about this in MC, in a safe environment, the bigger fear is we will always live like housemates and never be truly close and intimate like a married couple.
Thank-you everyone for your input.