T.S.
The thing about your kids is they are people and not things... (of course you know that) but the his and hers, mine and yours, thing isn't within your control when you're talking about relationships between PEOPLE.
It sounds like you're all getting along which is the most important thing.
I get that you want your blended family to feel like you would imagine a gigantic biological family... but it isn't... so it won't... period. He and his children have a whole history, memories, previous life together without you and your children... just like you and your kids have a history, memories and life together before them. Asking for it to all feel like "ours" is asking for those previous lives to become mute. That isn't what you really want, is it? Until everyone has more memories grown together than they do apart, it's unreasonable to expect that anyone will feel more like "ours" than "his and hers." But that's not a bad thing.
I honestly think that the best thing you can do for nurturing a natural-feeling, shared family is to let go of the idea that you want it to feel different and embrace what it is right now. Nurture and grow the relationships you have with his kids. Encourage the relationships between your kids and your husband, and between all the children. Your blended family is your blended family, and it's wonderful exactly as it is. Don't miss out because you're worried about what it's not. Love his kids, and love your kids, but don't feel bad if everyone's love isn't exactly the same in exactly the same ways.
HTH,
T.