[kwhitefoot]

Coding is not an end in itself. Your brother will need a reason to code, a problem to solve. That should come first and should be quite a small problem. Then choose the easiest tool with which to solve it. Operating systems, file systems, etc. are pretty much irrelevant.

You can do a lot with ancient tools like QBasic, simple graphics and so on. For more sophisticated things Python is a good tool because it has a simple syntax that is very readable and uncluttered.

Once he has made a few simple things like that run then if he has an Android device it might be worth installing Android Studio and trying to build some simple apps. There are plenty of tutorials with complete source code that can be examined.

And finally make sure that he understands that he can ask for help. The Net is full of information and people who can and are willing to help. I forget who said it: "There is no such thing as a stupid question, only stupid answers" so impress on him that when he gets genuinely stuck that he only has to ask on something like StackOverflow or many other forums.