Announcing pregnancies

So...my sister has been trying to have a second baby for 14 years, she had a miscarriage a few years ago, and is currently like 9-10 weeks pregnant. Well...I had a miscarriage last march, and we haven't been trying to get pregnant again...but I just found out today that I might also be pregnant...and if I am, idk what to do...

Like, do I tell my sister that I'm pregnant alone one on one?? We weren't trying it just happened...I've been having SUCH a hard time accepting her pregnancy, because I've been wanting another baby for a while now...but. I don't want to steal her thunder! This would be my third baby, and I just don't know if there's some kind of "etiquette" for this kind of thing??? Please help!!