I have two kids, Clark and Kent. While they're the same father, only one of them is biologically my child. They were born within six months of each other. The boys are currently six and for various reasons I have full custody of both of them. I didn't speak to any of my family for several years. We got back in touch in 2019. Due to the boys' ages, my family know I couldn't have carried both unless I have a gestation period of a hamster or the longest labor ever. I've explained to them how this all came to be, but my explanation, I neglected to tell them which is biologically my child. Due to my ex having a type, the other woman looked enough like me that boys could pass for twins. Same dark hair, blue eyes, pale skin, cleft chins, and dimples. My brother jokes they look like tiny Superman. People who know them refer to them as twins because aside from a few minor differences, they're practically identical. Frankly, if they were closer in age and I had full custody of them when they were born, I suspect I wouldn't mix them up a lot as babies. Shortly before Clark's birthday last year, my mom asked if she could see Clark's birth certificate. I asked why and she said she wanted to know the exact time he was born. So I told her. She asked if she could see the certificate anyway. I asked why. She said she wanted to check. I said I'm his mother, I know when he was born. Then she asked the same about Kent and we went on through the same conversation all over again. Mom eventually admitted that she just wanted to see the birth smotherers on the certificate, which isn't how it works, and I told her as much. This led to an argument where my stance was that I'm their mother, biologically is irrelevant. Mom says if biologically is irrelevant, it's not a big deal to tell her which is biologically mine. I said if she's so hung up on biology, then certainly it's a big deal to her and I don't want it to be a big deal, especially as the boys themselves don't know. Mom feels this is incredibly selfish, narcissistic, and overall wrong. She felt like biologically isn't such a big issue, then I should have no problem telling her whether Clark or Kent is my biological son, and that accusing her of potential favoritism or something similar with their biological grandchild isn't fair judgment and no actually reasoning for it. My boyfriend agrees I shouldn't tell anyone, at least until my sons have decided for themselves if they want to know and want other people to know. But my entire family agree with my mom that I'm being unreasonably selfish, that my actions now are more likely to cause issues than my mom's potential actions later. Am I wrong?