<human>: So this is a kind of twisted relationship, but I will try to give enough detail. This is a throw away for several reasons.
I started dating this guy casually we would go out and such nothing serious at first. He would bring his sister (Jane) around and her and I became really good friends. 
So a year and a half Ex and I are going well and way more serious, until I got a new job 5 hours away our relationship quickly went downhill and ended badly about 6 months ago. 
Over Labor day weekend while I was home he made a huge apology and I decided to let what happen in the past stay in the past and we had a fun time like old times. 
Then he did something that triggered me to questionably over reacted. Last I talked to him.

So Fast forward, to the end of September it is my friend Janes Birthday we made all these big plans to celebrate. I ended up getting really sick a few days before and had to go to the hospital and I completely missed her birthday. 
I'm finally coming home again and I wanted to celebrate her birthday the way she deserved in the first place, and I thought it would be an awesome to throw her a surprise party because she would never expect it and her SO ruined her birthday the first time around and so many people couldnt make it.
My Ex also missed her birthday because he was out of town. We all have the same group of friends now so not including him would be purposfully excluding him since he will know where all him friends are. While including him would make it seem like I can be civil.  So do I take the oppurtunity to get everyone together, or should I just come up with a new plan?

If I should.. How should I start that conversation? or Any other better ideas?

Can you summarize the given text in a few sentences?
<bot>: Should I have a party for my friend/ ex's sister and invite him or should I come up with a new plan. I also realized Im so confused about everything.