A middle-aged mama’s boy set to be sentenced Monday for murdering his uncle was actually the puppet of a greedy family cabal, a Long Island lawsuit charges.

The children of victim Jonathan Frankowski Sr. claim in the civil suit that their cousin, convicted killer Jonathan Roman, 44, was acting at the direction of his mom, Sandra Roman, and aunt, Annmarie Porter.

The sisters wanted their brother, Frankowski Sr., dead so they could inherit another $100,000 apiece on top of the $200,000 each they were already getting from their late mother’s estate, the documents charge.

Frankowski Sr. had been named executor of their mother’s will after her death in 2013 — and his siblings were furious that he was slow in probating it, his kids say.

“To them, this money is everything,” Frankowski’s daughter, Kim Delany, told The Post on Sunday, referring to her cousin and aunts. “To them, it was a fortune, and they wanted that money as soon as possible.”

Frankowski’s son, John Jr., added of his relatives, “Clearly they’re a bunch of bumbling buffoons.”

“Obviously, had it not been for [our investigation], I truly believe that Jonathan and the rest of the family, in their mind, thought they were going to get away with murder,” he said.

Credit: NewYorkPOST