My children are past the baby stage. I have a daughter (S) 7 and son (J) 3. My latest problem is how to handle it when the older one does not want her brother imitating her - or, in one recent situation at church, she became increasingly bothered by the 3 year old daughter of a friend. This child adores her and wants to be with her - but my friend (the mum) might not have seen how much it was upsetting S as she didn't intervene. Actually, her daughter did nothing wrong. I felt that S was unreasonable - but you are naturally on your child's side. I didn't want to have to leave mid service but it nearly came to that.
I am sensitive to the other Mum's feelings as I remember a similar issue when S was younger and another friend had older children who excluded her. I took the hurt personally and felt that I couldn't see that friend as it wasn't good to put my daughter through that.