Mom, please recommend a book about child psychology or something simil…

Mom, please recommend a book about child psychology or something similar. I can't handle it anymore, I don't know what to do. I have one son now, and haven't faced jealousy yet. But lately we spend a lot of time with my nephew, who is 4 years old. And my nephew is very jealous of everything, in terms of food and toys. He can hurt my son while nobody is watching, he might even lie on him, throw from a toy car, hit him, break his toys he plays with. And the son himself doesn't want to go and give up anything. A couple of times I said "no no" but heard "don't scold my son, let them sort