Weddingbee boards

I would invite your siblings, step or not. I personally would also invite your FIs aunt and uncle, but that's just me.

It's the path of least resistance.  SO it's something to consider.

On the one hand, since this stepsister, entered into your family as an adult, and that your father has only been married three years, I don't know that it's absolutely necessary to invite her.  You said that you aren't close.  It sounds like, you barely know eash other.  If she had been your stepsister since you were kids, that would certainly be a different story.  But stepsiblings that come together as adults, to me, aren't really stepsiblings, unless they happen to it off together.

However, if it's going to create big waves, or if your father and stepmom are paying for the RD, I think she should be invited. I's not worth setting a bad tone for two people.

If you are paying for the RD yourself, maybe you can politely say, it's nothing personal.  It's just for folks who are in th BP.  (I'm just wondering if not inviting her is being looked at as some kind of "I don't like you" snub.)

No you don't have to invite the aunt and uncle either, since they are not at all involved in the wedding.  Really, you don't want to make this another wedding reception.  I could see if they were OOT, but in town? I don't think so.