well, it's sad but this is why attitudes to career and money are important things to discuss early on. While some people on here with think you are wrong for having this view, I don't, but I think you are wrong to have waited until now to think about it.
It's so odd, so many couples, before making big commitment to each other will make sure they are compatible on attitudes to sex, religion, children, education, politics etc, but money and careers seems to be ignored. If he's been earning the same for some time, then I guess the amount he was bringing in when you first got together was comparable to ambitious friends/friend's DPs, so it wasn't as obvious he didn't feel that way, it's just that now it'll be noticable he hasn't moved up when others have.
As others on here have said, it's unlikely you'll change his attitude to career and money, so it'd be more productive to sit him down and say that yours should be the primary career for the family, so he goes parttime, is the one to do look after the DCs when sick etc. If he needs to take on more of the housework and running/managing the family/household so you can free yourself to work late/go in early to the benefit of you all, so be it.