I have 2 boys with 18 months difference between them so I know exactly how you feel. I think it important that we try to spend time with each one & they do their own thing separately, as well as doing things together. For instance, today one is going to a friends house & the other has a friend coming to our place. Sometimes when one is with a friend or at a party, I spend time with the other.
They spend a lot of time together & there are days when they don't stop fighting & driving me up the wall. Today they will spend some time doing their own things with their own friends, before we all go to a christmas party together this evening.
4 years old is a trying time. They start school & pick up all sorts of bad language & habits and are asserting themselves to get attention. Just make sure you don't give in as it is crucial to get the right basis before they get older & bigger.
Try asking why he says hates you. Tell him you love him & that he is upsetting you when he says that. He might be copying other kids around. Ask him if he would like to be told on a daily basis that you hate him & see if he can understand how it feels to be on the recieving end.
