So my almost 13-month-old bites and he pulls his four-year-old sisters hair and he thinks it’s funny. He continues to bite my nipple. Even though I tell him no it’s not funny and it’s not nice. I have tried the act like I’m in pain by crying method. I have tried biting him back I have also pulled his hair a little bit to let him know that it hurts. And I also sent him in his pack and play when he goes to bite or pull hair. & he cries the whole time in the pack n play . He literally laughs when I go to pull his hair or bite him back. He doesn’t cry at all