Traditionally, the wedding was paid for by the bride's parents and so the wedding invitation wording reflected this:
Mr. & Mrs. John Jacob Smith request the honor of your presence at the marriage of their daughter, Julia Jennifer Smith to Joseph Alan Brown Saturday, the twentieth of July two thousand and two two o'clock in the afternoon First United Methodist Church, Springfield, Illinois
Today, however wedding invitation wording has become an art in and of itself. Many couples pay for their own wedding and so they begin their invitation with:
Julia Jennifer Smith and Joseph Alan Brown request the honor of your presence at their ceremony of marriage Saturday the twentieth of July, two thousand two etc.
Sometimes, the brides parents still pay for the wedding, but they don't want to leave the groom's family out:
Mr. & Mrs. John Jacob Smith request the honor of your presence at the marriage of their daughter, Julia Jennifer Smith to Joseph Alan Brown, Son of Mr. & Mrs. Wallace Joseph Brown etc.
Increasingly, families are a conglomerate of a lot of different relationships from step-parents to divorced parents. When it comes to wording your invitations with these relationships in mind, simply do what you feel is best. If you would like to know the proper way to word your invitation for each of these cases, check out Emily Post's Wedding Etiquette.
If you are not worried about etiquette, however, then I would recommend wording your invitations in whatever manner feels right to you and your fiancÚ.
For example, if both of your parents are divorced and all are contributing to your wedding or you simply want to recognize them all try:
Mr. John Jacob Smith and Ms. Leona Green together with Mr. Wallace Joseph Brown and Mrs. Anna Elizabeth Grainger request the honor of your presence at the marriage of their daughter and son, Julia Jennifer Smith and Joseph Alan Brown etc.
In addition, many couples are throwing out the "request the honor of your presence" and are going for a less formal approach:
On this day we will begin our journey of marriage and would be delighted if you could join us at the wedding ceremony of Julia Jennifer Smith to the love of her life Joseph Alan Brown etc.
Just remember, your wedding invitation is the first thing your guests will see in regards to your wedding and thus reflects the style of your wedding. If your wedding is formal and more traditional, you may want to take Emily Post's advice. If, however, your wedding is less formal or non-traditional, feel free to play with the wording to make it reflect your wedding style!