Problems with 4 year old?

I am 20. My parents died and left legal guardianship of my 13 year old sister, 4 and 9 year old brother. My gf is also pregnant. The 4 year old seems to think that he runs the house. If I tell him no swimming today he will go against me and jump in the pool. I tell him that that is a no no because he could get... show more I am 20. My parents died and left legal guardianship of my 13 year old sister, 4 and 9 year old brother. My gf is also pregnant. The 4 year old seems to think that he runs the house. If I tell him no swimming today he will go against me and jump in the pool. I tell him that that is a no no because he could get hurt. If I tell him it's time for bed he'll tell me no it's your bed time. At dinner he throws his food and I take it away and say if you can't eat like a big boy you won't be finishing your meal. If he continues to throw it I take it and put it in the fridge for later. He hits me and back talks. He does have a thing with cursing. I have given him a few swats on his butt for going in the pool without anyone watching and for disobeying me and throwing his food constantly. I also take his cherished toys away and put him in timeout. He also likes to run in the street and let go of my hand when we go shopping. I have no clue what to do about this. It's constant and I have gotten calls from his day care center telling me that he picks on some of the kids there and throws fits when they say no or when they don't go outside. He also does that here. Please help.

P.S. I have this question in parenting too but not many people are answering. I really need help and advice thanks.
Update: Thanks for all your answers. Right now he is taking a nap cause he is quiet cranky. Thanks fo all your sympathy. Who ever said giving them to someone else. Im sorry but I can't do that to them. They just lost their parents they can't lose another family member. I do think he is grieving but he was acting... show more Thanks for all your answers. Right now he is taking a nap cause he is quiet cranky. Thanks fo all your sympathy. Who ever said giving them to someone else. Im sorry but I can't do that to them. They just lost their parents they can't lose another family member. I do think he is grieving but he was acting this same way when they still were alive.
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