Max Regnery is the owner of Pine Hollow Stables. He knows a lot about horses and the Saddle Club cares for Max and tries helping him out sometimes (but often just create a large mess, e.g. in the episode "Set Up").
His mom is Elizabeth Regnery, who helps the horse riders out of problems. In Season 1, his girlfriend is Deborah Hale, and he plans to propose to her in "The First Refusal" but Deborah proposes to him first. He says yes (of course) and the two get married in "The Bridle Path Part 2".
In Season 2, he goes to a prestigious French riding school and is absent for the majority of the season (but not ALL of it). His cousin Andrew Regnery takes care of Pine Hollow during his absence.