Fair point about the hyphenation. OK, he’s out.
I am “happy” to come up with an 8-8-8.
Pharrell Lanscilo Williams
William Schwenk Gilbert (of “and Sullivan” fame).
I know that this thread is for real people, but I’m throwing in a fictional character. From Catch-22 there is Major Major Major Major.
Similarly, but real, there was a cricketer called Neville Neville. I don’t know his middle name (if he had one), but I like to think it was.
I went to school with a kid named Bob Van den Bos.
I looked up James Brown (the singer) and James Brown (the football player) to see if either of them had five-letter middle names (they don’t).
But, while doing so, I discovered James Cooke Brown, a 5-5-5, who was a bit of a polymath: he was a sociologist, science fiction author, creator of an artificial language (Loglan), a boat designer (he developed a particular design for a trimaran (three-hulled sailboat)), and creator of the board game Careers.