I want to announce my pregnancy at SIL's gender reveal party
Do you have a reason you want to announce it at your sil party?
My SIL is not married and I am happy for her that she got pregnant by the man she was involved with. I'm announcing my unborn child's gender at their party because my SIL told me it's a boy.
It's wrong to takes someone's gender reveal party as your own. Find your own time and do it there.
I want to go to their party and we both know that
It's fine to attend her party, but don't steal her thunder. This is her big day and her day to get the attention. It's rude to want to upstage someone's event.