When this woman tells her nieces the truth, she asks Reddit:
About 2 years ago my SIL 27 became extremely ill & passed within a few months of her diagnosis.
Prior to her passing, I 22 F flew out to go help her & my brother 29 with their daughters now 6 & 8 so they didn’t have to worry about the kiddos. During that time they became attached to me.
Her passing was difficult for all of us, especially knowing how wonderful of a mother she was to the girls. It’s been 2 years and it’s still hard for my brother to process it.
My brother said he didn’t want to tell his daughters & I could tell seeing them broke him because they would often ask how their mom was doing… so I suggested having the girls move in with me & my fiance until he was in a better place.