Step brother fears he may have had a hand in disposing of Drew Peterson‘s fourth wife, Stacy’s body!

Thomas Morphey, the stepbrother, told the Herald News that he thinks Stacy, 23, was in a blue barrel he helped remove from the Petersons’ home in Bolingbrook, Ill., and then put in a car.

Stacey Peterson has been the subject of an ongoing police investigation since her disappearance in 2007.  Her husband, Drew, was the chief suspect in a police and grand jury investigation but has never been charged with her suspected murder.

Reason?  Hard to make a murder charge stick without a corpus delecti –the body of the victim.  Even Nancy Drew can tell you that.

Morphey alleges that Peterson asked him to move the barrel after a conversation that Morphey said Peterson would like to murder his wife’s boyfriend.

"We went to that park to discuss Stacy cheating on him, and he had to take care of the problem," Morphey told the newspaper. "I didn’t think for a minute he was going to try to kill her."

But after Stacy disappeared cops exhumed the body of Drew Peterson’s third wife, Kathleen Savio, ruling her drowning death a homicide.

Peterson wasn’t charged with that murder either.

Morphey has been offered immunity by the police but has yet to talk to the grand jury.

As to Morphey’s claim he may have disposed of Stacy’s body hidden in a blue barrel, former cop Drew Peterson charged "He’s hallucinating!"