All Answers

Mr. and Mrs. *Step-Dad and Mom's last name*
and Mr. and Mrs. *Dad and Step-Mom's last name*
request the honor of your
presence at the marriage of
their daughter
Bride with last name
to
Groom with last name
son of Mr. and Mrs. FIL's
(I hope that wasn't too complicated) I found it on http://www.invitationconsultants.com/samplewording.aspx?p_subcategory=3

That's a tough one because the names listed at the top are traditionally the ones paying for it. If your mom is OK with the suggested wording from Danielle that would be the way to go except leave out the word "and" inbetween the sets of parents names just stack them instead. If she's not OK with it then I'm not sure what to suggest. If your dad is walking you down the aisle to give you away then he (and step-mom) should be on the invitation. If they are not part of the wedding at all then you could leave off dad & step-mom & include their names on the program instead.

@Invitation PLace, what's wrong with the "and" it is usually included as a separate line on all the samples I have. I think Danielle's suggestion is perfect.