How to not invite extended family to a micro wedding

I’m having a micro wedding and the only guests are immediate family, grandparents, and my fiancés 2 cousins and aunt. They’re immigrants from a really far away country and they’re basically immediate family. My extended side of the family is in a big fight and half of the people are not talking to each other. So I’m ok with inviting only my fiancés 2 cousins and aunt.

In order for my step dads mom to attend, she would need to be with my step dads sister (and her husband as her plus 1). I’m in a dilemma because I want her to attend, but my parents are saying if I open it up to my step dads sister then I’ll have to invite all of my moms siblings and the rest of my step dads siblings (and then probably all of my biological dads siblings). My fiancé and I really want to keep the wedding small bc we’re both very shy people and I know if we invite more people we will not enjoy the day bc we’ll be stressed out and uncomfortable. Any ideas on how I should handle this? Thank you xx