Just a friendly correction, as I have seen the mistake twice. The word "pianoist" should be "pianist."
As it relates to the subject at hand, what your little bro is doing right now is fine, but as a believer in basic musical training--even if you have to teach yourself, I would encourage you to get a book of scales, arpeggios and cadences. (Alfred's Complete Book of Scales, Chords, Arpeggios and Cadences) The cadences will aid in learning chords and the book, overall, will offer a technical and foundational knowledge of piano playing.