I am putting this in chat rather than aibu as hoping for proper discussion.
My mum tries to make things equal between siblings all the time. We are now in our 50s but this has been since we were kids. It sounds like a nice thing to do but actually it pitted us against each other, so we were always comparing against each other. eg if one of us had something then the other had to, not because we cared but because my mum would be making a big fuss of how equal she was making us.
But this has carried on to our kids - her grandkids, to the point where every thing becomes a thing that has to be spread equally. For example, if my son - let's call him Jack - says he has done well in music at school, my mum will respond with 'Jill is very musical too' - Jill being my brother's kid. This happens all the time. To the point where my ten year old said why does nanny never let me say anything without saying my cousin does that too?
It even happens to me even though I am a fully fledged grown up. I had a work event to which an audience was invited. Someone I worked with said you must be very proud of your daughter ie me. Oh yes, said my mum, I am proud of all my children. Yes, of course she is, but this was my work event and actually about me.
I don't even know if this makes sense. It drives me mad though - surely just occasionally let people shine as individuals. We know it doesn't mean less love for the others.