A couple of kitten questions?

The best answer is to ask the vet. You could try limiting the larger kitten's number of daily bottles, but make sure there is always food available for him to eat. I keep a bowl full of food all day long for my cats. They have never over eaten. Over-eaters usually result from not getting enough as a kitten. The larger kitten my be more immature than the other and needs "mommy" still. The vet would be my first contact, though. Vets usually have more experience and answers for these kinds of questions, plus the phone call is free.