回复：求助——怎样化解幼小姐弟矛盾？

I have three kids, they are 8, 4 1/2 and 2. They love each other every much. Of course, they argue; they push each others (sometimes). This is normal for kids. However, as a mother, I always make sure they have exact same treatments. Three sets of everything. For example, If I need to buy toys, I will make sure everyone has one (they choose what they want). Baby food, they all can eat if they choose.
I will suggest you spend more time with your son and let 姥姥 姥爷 take care your 老大. Make sure you tell them that you are everyone's mom and you love them equally.
Good luck.