My brother’s wife used a sperm donor because my brother couldn’t have kids. They have never told the kids that my brother is not their biological father. The kids are now in college. I have always thought that was a mistake and that the kids might be really messed up psychologically when they inevitably learn the truth.
“My brother’s wife used a sperm donor... “
I am sure your brother and SIL thought that keeping this a secret would ensure that the children bond with your brother. However, when or if the children do find out... they are sure to feel like their entire lives are a lie. I am not sure if your brother/SIl received any genetic information like heart disease, diabetes etc... but knowing one’s genetic history (when possible) is helpful. This is certainly tricky for your family!