I'm not allowed to invite any of my friends to my parents wedding. (My dad and stepmom's wedding) is this fair?

My dad and stepmom are getting married on July 1st. They’re both inviting about 25 people each. I have 3 sisters. One that’s biological and two that are step. At the moment I’m a bit miffed because my stepmom said that my one sister who is 22 is allowed to bring her boyfriend and her best friend, my other sister who is 33 is allowed to bring her baby’s daddy. Basically her and this guy hooked up on tinder and had a baby and he comes to the house twice a week, but they’re not in any sense of a relationship, and then my other sister who is only 7 gets to bring her best friend and the best friend’s entire family is coming. Yet my stepmom won’t allow me to invite anyone because my friends don’t hang out at the house enough. I’m the type of person who likes to go to the lake or go for a hike or on a road trip with my friends not stay at home all day and play card games and drink. So is this fair? Do you guys think I should bring a friend anyways without their permission? Especially since everyone at the wedding will have someone besides me.