So I could really use some input! My fiancee and I are each products of divorce. Both of his parents are remarried, get along well with each other, and are willing to help us out a little bit financially for the wedding. My father is remarried, my mother is in a long-term unmarried relationship, and I consider the guy a full step-father. My parents DO NOT get along. My father is pitching in somewhat, but my mom and both of his parents are helping out a lot more. I think we should include all or none of the parents on the invitation, but I don't want to slight the future in-laws or my mom since they are all being very generous. We are paying for the bulk of everything, but we really couldn't dp this without their contributions.
In summary, my questions are:
Do we include all the parents on the invitation?
If so, do I include my mother's boyfriend (that will be 5 different last names on the invite)?

Just to explain where I am at, we've been engaged since last June, and we have only recently decided what city we're having the reception in (since his mom is in another state).

Thanks for any help you can offer!