Alek bites, and the little devil will always make sure I'm not around to see because he knows he will be in trouble... his sis is not such a good tattle-tailer so if he bites her and I am in the other room, she will just scream and I have to run and check for bites and put him in timeout... I just bought a book "teeth are not for biting" to read to them. Sometimes he is just playing or teasing, and she will freak out too, so it's hard with him. G was never a biter until Alek started biting her (probably when he was first teething ) He's never bitten anyone else but the only other kids he plays with are at Gymboree and there are always many adults around so that probably compels him to be better behaved Gabi hardly ever bites him because she knows she will be sent to her room... her timeouts always last way longer than Alek's because she starts one of her melt-downs and I won't let her out till she chills a bit...

So, sorry no advice other than maybe the book if you think it'd help. It comes in a board book version, which is what I got.