O'Brien's Restaurant on Wells Street in Old Town. (José M. Osorio/Chicago Tribune)

A private business feud between the founder of O’Brien’s, a longtime Old Town restaurant, and his son has escalated into a lawsuit, throwing into question control of the family’s businesses.

Daniel O’Brien Sr. accuses his son, Peter O’Brien, in the suit filed Thursday of improperly gaining control of the various family businesses, including real estate, nursing homes and a golf course in New Buffalo, Mich., called Whittaker Woods. He seeks the return of stock holdings and other monetary damages.

The two got into a dispute last year over an undisclosed issue at the golf course and have been unable to resolve their differences, the suit said.

“After 33 years of working with his father, Peter is obviously very disappointed that his father chose to file a lawsuit over what is essentially a family matter,” Peter’s attorney, Richard Prendergast, said in a statement. “Unfortunately the complaint is filled with factual inaccuracies concerning events Dan O’Brien has either forgotten or chosen to mischaracterize.”

Prendergast said his client will “vigorously defend” the allegations against him.

The allegations stem from estate planning Daniel O’Brien started in the early 1990s to transfer ownership of the businesses to his heirs that would minimize estate taxes when he and wife, Mary, died. In 1994, they formed several limited partnerships and corporations and gave Peter, one of their six children who was most involved in the businesses, minority ownership interests in them, the suit said. Three of their children have died.

The parents’ goal of the estate planning was to transfer ownership of the businesses over time but not control until they died, the suit said. Peter handled most of his parents’ legal affairs as their fiduciary, the suit said.

“Only recently, in early 2009, Dan discovered that Peter grossly abused that trust by causing Dan and Mary to execute written instruments that gratuitously transferred legal control of the family businesses to Peter,” the suit said.

The 86-year-old father alleges that Peter, 54, fraudulently concealed the “true nature” of the documents that transferred control. Prendergast denied the fraud claim.

“Claims that Peter engaged in any of kind of fraudulent or deceptive behavior are demonstrably false and when all of the facts come out it will be clear that all allegations of misconduct are baseless,” Prendergast said.

Peter O’Brien is a well-known businessman in Chicago. He has served on various boards, including the Metropolitan Pier and Exposition Authority.