If your brother spends his points in it, why should you then keep him from using it? You guys can agree to a house rule that no one can get it if you want, but if not, then he should be able to use it.
Just about everything in the recruiting tree is WORLDS better than anything in the coaching tree except for "big game" and "4th quarter (or whatever it's called) anyway so I'd invest in that.
Also, while I don't use coachstradamus, I'm 95% sure that it only tells him the type of play (IE. run, pass) that you called in the huddle and doesn't tell him what you audible to/hot route to.