You'll love him. Of all my uncles, he's easily the warmest and friendliest.
Uncle Mike is Shawn's uncle, and Chet's brother. He is a very tall and imposing man who owns a motorcycle repair shop. Shawn got him to repair Mr. Turner's bike at a fair price despite his efforts to raise it. When Shawn was making a video birthday card for Chet, Mike was the first Hunter who Shawn told.
In Season 2, Episode 10, "Sister Theresa", the same actor; Herschel Sparber, plays T.K.'s delivery guy, Tony.
Since Jack is Chet's son, that would make Mike and the rest of the Hunter clan Jack's relatives as well.