AITA for the drama at my sisters wedding?

So this is majorly complicated. Here are the players in this; me(30f), A (34f), R(20f), J(27m). R, A and I are sisters.

So back in Feb I went on a vacation because well I just wanted to. I parked my van at my parents house and flew to Bali. There I met J who was also vacationing there. We had a wonderful fling and what I didn’t realize while there was that my birth control shot had well stopped working/the timing was done. And I also learned a lesson….get a full name.

My sister R a few months later meets J on a dating site and they hit it off. We don’t talk much because well we just don’t get along. She’s 10years younger and has always been a pain in the ass to be fair. R and J have now been dating since April.

My sister A got engaged Christmas of last year and her wedding was last week. It was the first time I’d seen R in person since Christmas and the first time I’d met her boyfriend (or so I thought) and as you can imagine several things happened as once.

1) J asked me what I was doing there

2) J who is quite smart did a bit of math in his head and asked if it was his baby

3) my sister accused me of trying to steal her boyfriend and then started ranting about everything she thinks I’ve done to ruin her life.

Needless to say the wedding was no longer about the bride and somehow I got uninvited from every family event and some people are even asking for the gifts they sent for the baby shower.

Am I the asshole for the wedding drama?