A.L.
First of all, you probably shouldn't get your son to take something away from his little sister. You should do it. It probably create confusion for her AND him. She doesn't know if he's coming to take something away from her or help her. As for the hitting and biting, I began TIMEOUT with my (almost) 3 year old at 1 year old and she grasped the concept quickly. Anytime she hits or bites, immediately remove her from the situation and put her in TIMEOUT. I use a little chair (her size) and I turn it around facing away from the open room. I sit her in it, come down to her eye level and explain to her she must sit here for 2 minutes (1 minute per year of age) and tell her why. After the time is up, come back to her eye level and have her apologize to her brother and give him a hug. Good luck!!