Second baby

So my husband and I just found out that I am pregnant with our second. We had always planned on trying again once our daughter turned one, so that’s what we did and wouldn’t you know, it happened immediately! We are so excited but also very torn... my SIL has been struggling with infertility for almost two years now and has been doing treatments that have not taken yet. I feel almost guilty that I’m pregnant for the second time and she hasn’t been able to get pregnant yet. How do you think I should approach the subject with her and my brother? I don’t want it to seem like we are bragging or rubbing it in their face. TIA!