This reminds me of something I read awhile ago about the Inuit. Their children start from when they were practically infants, around 2 to 3 years old, learning how to use small knives. Something to do with impressing the skills of a tool, that was intrinsic to their survival, as soon as possible on the young. I could remember the caption for a photo of how a couple of small children were carving whale blubber to feed themselves from the carcass. Cute.
Anyways, I digress... depending on the age of your brother, I favour a working knife over a tactical one if I was in your shoes. Much more versatile.
Sounds like the kid is into folders. Off the top of my head, maybe something from Cold Steel's Voyager line ( non serrated ) would be a good start. They have sales on their items all the time online at the various dealers.
Anything else, other than Spyderco, and the price keeps climbing quite steep. Would like to see what others think.
Just my 2 cents.