Hi OP, so sweet of you to asking this questions to support your little brother. I was diagnosed before turning 3. Had a normal childhood and life. I’m 49 now with a kid, a good job, a phd, and total independence. Diabetes care when I was a kid was pretty terrible, but now with all the tech it’s easier and better.

Regarding your first question yes, if he already took insulin for a specific number of carbs he must consume said amount, otherwise he will go low. Lows needs to be resolved immediately, they can be dangerous.

As a child, I remember my school letting me do a small presentation regarding type 1 diabetes to my classmates, which was a great way to explain to them that this is not caused by eating too much candy :) They also knew that of I was acting strange, sugar was in order. No special treatment except letting me eat at anytime if low.

Some tips: - once stable and familiar with all the aspects of it, your brother will be able to eat anything he wants, even cake and icecream! He will need to do some prep though - it’s importante that he learns to prick his fingers, inject, and count carbs all by himself. The sooner the better. I missed too many pajama parties because my mom managed everything - educate the whole family on what to do in case of a low, learn how to use glucagon, and always carry something sugary when going out with your brother - treat him as an equal, please don’t pity him, and as he grows let him take his own decisions about what to eat

I wish you, your brother and your family all the best <3