Music producer David Gest - a close friend of the late 'Beat It' singer - is demanding damages from Julien's Auction House for attaching 'from the collection of David Gest' to items they sold shortly after the pop icon's death in June and has enlisted the star's sibling to boost his case.
David claims he never owned many of the auctioned goods - including a Platinum RIAA Record Award for the album 'Thriller' - and that he never gave the auction house permission to use his name.
Speaking in support of David, Tito said: "I am amazed an auction house like Julien's Auctions would use David Gest's name to sell an item that was not his.
"There are a number of the items that they listed in their Michael Jackson catalogue on June 26th and 27th that never even belonged to David Gest.
"I will also testify in court that this RIAA Award Disc for Thriller Presented to Steve Manning never belonged to David Gest".
Lots at the auction included a signed Jackson 5 album, which was expected to fetch up to $600 at the auction, but sold for $33,750, and a childhood painting done by Michael of Mickey Mouse and Pluto, which sold for $25,000, 25 times more than expected.
David said: "So much for the statement by Julien's Auctions' lawyer that they are 'good honest folks'.
"I'm sure this will open the door for many others to question items they have sold."
Steve Manning, a former publicist for the Jackson 5, has also pledged to give evidence if the case comes to court.
Julien's Auctions' denies any wrongdoing and Darren Julien, who runs the auction house, has filed a federal lawsuit to ask the judge to see through David's legal action.