I think the main question first should be are you ready to take care of your brothers snake. Kids (not all of them, but most) can loose interest fast, an 11 year old is not financially able to purchase an enclosure (or any husbandry item) for that matter and food on a weekly basis, as well as maintaining a clean environment, so I assume even though you are getting it for him, it will be an addition to what you have. If that is the case then I would say get something that interests you both. I have had corn snakes that never stop moving and I have had others that are completely calm. The only problem I would see with a ball python would be the potential for them to be picky eaters. Does he have any reptile experience, what does he like?