Etiquette on not inviting my step-sisters partner to the wedding...

Years ago, it was unheard of to invite one half of a couple but not the other, but it does seem to be becoming more common now. However, it is something that does still carry a high risk of offending the couple, so you really need to weigh up the advantage of not inviting step-sister's partner against the possible offence caused to step-sister. If you decide not to invite him, I would suggest it might help if you called step-sister before sending the invite, to explain that you only want people you have actually met to be at the wedding as you are so limited on numbers. She might still be upset, but it's less likely that if the first she hears about it is when her invite turns up without her partner's name on it. Because most immediate family are going to assume that they AND their partners are invited to a wedding.

Wow, this is a tough one! I totally get your fiancé’s point. With such a small wedding and a tight budget, every person counts. Honestly, it sounds like this boyfriend is barely in your life. I'd probably lean towards not inviting him. You could always have a smaller get-together later and invite him then. It's like in agario when you're small and see a giant blob coming – sometimes you just gotta strategize and avoid unnecessary risks, and sometimes go big later when you are bigger!

I know the struggle! but for something so intimate, I feel you will regret inviting him. he will be in all your pictures and just mention to your step sister that you only want people there that both of you have met/have a relationship with because of how small the wedding is. if she is offended by this reasoning then that is a her-problem not a you-problem.