My Fiancés Brothers Baby died :-(

Brittany • Mommy to a wonderful 12yr old boy, 9yr old boy 7yr old girl 6yr old girl and 3yr old girl. Due March 11th 2023 with a boy.
I'm lost at how to feel. My SO's brothers baby was full term and they lost her today :-( his Mom is devastated it was her 1st grandchild. I feel selfish to be happy about my baby now. I dont feel right putting my happy news out there when people so close to me are hurting :-( how do I deal with this and not feel like I'm being insincere?