To make inner peace with yourself, try not to compare. Your baby will eventually know who is nice to them and who is not. Most importantly your baby is well loved by mummy and daddy.
Try to ignore. No point feel angry or upset over such bias attitude for the kids. kids are young they don't know. Kids feed on our feeling. ignorance is bliss.
I'll ignore and don't care. If I get affected by it, it does me no good. It won't change the situation either.