There is no reason a child can't be off the bottle by 12 months old. They don't need all that milk! I had a girl start my daycare in sept. she was only 11 months at the time so was still on bottles (formula) and wasn't eating much at all. I kept giving her a bottle for the months of Sept/Oct/Nov. In December I mentioned to mom that in the new year I would like to get rid of the bottle all together. I know mom wasn't really on board with it but she did agree that it was my house and I could go ahead. I started in December by giving her the milk in her sippy cup. Sure she didn't like it but it wasn't long until she started eating more food. In the new year I told mom I had her off bottles here and that she didn't need to bring them anymore. I am pretty sure they still give her multiple bottles at home although she doesn't need them and would likely eat more if she didn't get so much milk. I also had a 15 month old start with me in October. I also had him weaned off by December. He ended up being sick for a week and mom wasn't giving him a bottle at home while sick so she decided to just keep him off it.

Just tell mom that at your house he will get his milk in a cup. If he has a cow's milk sensitivity would you be willing to buy different milk for him? I imagine if you asked mom to supply him milk she would just bring him formula. There is no need for formula and if she wants to feed him it at home then so be it but at your house he doesn't need it.