Hi, there's a million different ways of getting into the business and I'm sure you'll get a million different suggestions. I started off not far from you - Port Arthur, takes me back thinking about it!
Might not be a bad idea to trawl the marinas around Houston/Galveston and pick up some daywork/delivery work in the area - test the water, see if he really likes it and pick up some basic skills. Too many new crew expect to jump on a 200' without knowing a **** thing, and there's no substitute for good basic seamanship.
There is a decent school in Houston if I remember correctly - merchant marine - but I'm ****ed if I can remember the name. If your brother wanted to go ahead he could do his STCW 95 basic safety courses there.
Hope that was a little helpful.