The family of a Manhattan comedy club owner stabbed to death in his tony suburban home didn’t know his alleged killer — their au pair’s brooding ex-boyfriend — had a key to their house, they told The Post.

Nanny Karen Bermudez-Rodriguez “never disclosed to the family that there was a conflict between her and (ex-boyfriend) Joseph Porter,” a friend of the family of club owner David Kimowitz told The Post.

“The Kimowitz family was unaware that Joseph Porter had a key,” the friend said. “Karen was aware he had a key and asked him to give it back.”

Kimowitz, 40, and Bermudez-Rodriguez 26, were stabbed to death early Saturday.

Porter, 27, was later arrested in Newark and charged with two counts of murder.

Neighbors said Porter reportedly stalked the house for hours on Friday, while his ex hosted a party inside the home. At about 6 a.m. Saturday, he allegedly used the key to enter the house.

Police said the Elizabeth, N.J., resident first fatally stabbed Kimowitz — who owns The Stand comedy club — then chased Bermudez-Rodriguez outside the home and stabbed her to death.

Neighbors said she could be heard screaming “Oh my God!” over and over.

“I sleep with the windows open,” said Kathy Cantwell, 63, who lives next door. “At 6 a.m. I heard it. It was piercing. Blood-curdling screams over and over.”

Kimowitz’s wife and two young daughters were away for the weekend and were not in the home when the attack took place.

A 20-year-old jogger saw the bloodied nanny in front of the house and called police, fraught 911 calls obtained by The Post show. She was pronounced dead within the hour at a local hospital.