My mom is paying for my wedding. It'll be
"Mom" requests your presence.....
at the top, and underneath my fiance's name in the middle, we're putting
son of "future in-laws"
I don't think it really matters these days, other than the person that is paying for it (or paying the most) goes first. I originally hadn't put my fiance's parents on the invites, but my future MIL asked me to, just because she's afraid that some people may look at the invite and be like, "Who ARE these people??!!"