I always wanted three (I am one of four), DH is adamant he wants two (he is one of two). I am currently pg with DC1, after early mc last year, and TBH I am now thinking two is just fine - have had a really difficult pg so far, extreme 'morning sickness'. I may change my mind - and would need DH to agree and make sure we are together on the decision, as I really see out marriage as partnership, and should come first. This is because, I have seen friends push and push, and it really affected their relationships. One friend, about to give birth on Sunday, her DH is totally detached. Has been to none of her scans, does not want to be there when she gives birth and wants to be in the pub 'wetting the babies head', is still out getting drunk when she is about to drop etc, and because she insisted on the baby, he is like 'you go what you wanted' etc. It is awful to watch, and we (me and DH) both find it very odd, and worrying. But every man is different - I know the yearning for a child and how strong it can be, but my mother once told me in private that four is an awful lot of work, and very expensive too, and three was a great number, not that she doesn't adore number four. So, still part of me wants three, and you never know what will be. I would have a very, very open discussion, pour your hearts out, and see what comes out. I think it also depends how old your little ones are - maybe he just wants to get them both to a certain age, and then think of number 3?
And I am by no means belittling your need at all - but do you have pets? We have a little dog, who is basically like a mini child half the time. If you love animals - maybe this could be something of a compromise for the time being?
Good Luck!!!