OP I am sort of in the same situation as you, but have been with DP for 5 years and have no DC. I made it very clear to him within the first month of meeting that I want a marriage (not necessarily a wedding, a commitment ceremony would suffice) and children and that only one or neither (assuming there are no medical complications) was not an option with me. He stayed with me, we moved in together.
Still no marriage or babies. We used to argue about because I couldn't understand it, why doesn't he want to marry me? I could give him reason after reason for wanting what I wanted, whereas he couldn't do the same.
Anyway, a year and a half ago it appeared to Dawn on him that I would actually leave him if he didn't want what I wanted. He became very upset because he said he loved me but he wasn't sure he wanted those things and thought I would leave him. I said, calmly, that yes I would. I know what I want and I will compromise on lots of things, almost everything, and have done on lots o things I thought I never would, but those two things are so important to me that I would prefer to be single and have the opportunity to meet someone with whom I am more compatible than stay with DP, who I adore.
He told me he would marry me. He told me we could have a family. A year and a half has passed and nothing, I had a miscarriage in February and he was 'relieved'. He has another year, tops, and then I will have to call time. It seems silly to waste both our time when we are not both working towards the same end goal. I deserve someone who wants to give me those things and he deserves someone who wants what he wants.
I haven't mentioned it again, though, since our conversation. Anything else I say now will feel dry much like I have forced him into it and I don't want that, so he has to want to. But in a time frame. That's why I think you should nt mention it to him again, and figure out if it really is a deal breaker, because it categorically is for me.
Whoops, sorry for the hijack 