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He is the Battle Tower Tycoon Palmer, your rival's father. When you first meet him, he seems to know you since he predicts your rival coming. When you actually battle him, he'll tell you the story.
You must go to Single Battle in the Battle Tower rooms and beat it 3 times in a row without ever losing. (Like Battle Frontier in Emerald) On the third run, instead of the normal seventh battle, the Tower Tycoon will challenge you with Dragonite, Rhyperior, and Milotic IN NO SELESCTED ORDER! If you win, your Battle Tower team used on that run will get the Ability Ribbon and you will receive a Bronze Trophy for your secret base. Do this again but 7 times and on the 49th battle, you'll fight him again but he will use Heatran, Regigigas, and Cresslia instead. This information was taken from serebii.net/diamondpearl/tower.shtml
I don't think you mean Tycoon as you never actually run into him, you just fight him in the Battle Tower.
Did you mean Buck? If so he had red hair, supposedly he is Flint from the Elite Four's brother, you'll meet him again at Stark Mountain.