A heartless home health aide and her family allegedly commandeered a patient’s Upper East Side apartment, refusing to let her daughter in after the 103-year-old woman’s death — and cruelly threatening to flush the old lady’s ashes down the toilet if she tried, according to court records.

Incredibly, the alleged squatters claim they have “succession rights” to the East 86th Street pad because they were like “family” to the dying woman, according to court papers.

Tatiana Abello, her mother, and sister have been living in the $ 2,088-a-month, two-bedroom, rent-stabilized pad for 18 months and counting since their elderly charge, Verra Katz, died in August 2021, legal papers show. It’s unclear if they’ve paid any rent.

Tatiana Abello was hired in 2016 to help care for Katz, a one-time big band singer who performed under the name Verra Stuart, said her daughter, Alayne Skylar.

Eventually, Abello brought her sister Victoria and mother, Olympia Oviedo-Reyes, into the 1,221-square-foot abode, said Skyler. The women hail from Colombia.

“I loved these people. I had a relationship with them because they took care of my mother,” Skylar, 65, told The Post.

Things changed about a month after Katz died, said Skylar, who lived in the apartment for more than a year during the pandemic.

“We talked about what the exit plan was going to be,” Skylar said of her conversations with the Abellos. “I bought them dinners, I bought them gifts.”

Then one day she visited and “there was a slider bolt” on the door, she recalled.

The Abellos allegedly refused to open the door for Skylar, who had been paying the rent. They also refused to let cops inside, Skylar claims. The NYPD typically will not interfere in housing disputes, leaving the cases to the courts.

“They were threatening to flush my parents’ ashes down the toilet,” claimed Skylar, who accused the Abellos in court papers of refusing to return her parents’ remains.

Left with no other recourse, Skylar took the Abellos to Manhattan Housing Court, where by December 2021 they agreed to hand over the ashes of Verra and Skylar’s father, Ralph Katz, an editor for The New York Times who died in 2003, records show.

But the proceeding was inexplicably dropped after the ashes were delivered, leaving Katz locked out of her childhood home and unable to access her mom’s belongings, according to court papers.

The landlord of 305 East 86th Street, where apartments similar to Katz’s rent for $7,000 a month, is now suing the Abellos and Skylar in a bid to recover the home. And they want the Abellos to start paying rent.

“The tenants should not be granted a ‘windfall’ and be permitted to escape ‘rent free,” the landlord argued.

But the Abellos claim in court papers that they are now the “legal, rent-stabilized tenants.” Their “loving, family-type relationship” with Katz before her death gives the Abellos “succession rights,” their lawyer, Alan Goldberg, argued in a Manhattan Housing Court filing.

A baffled Skylar insisted, “They were never on the lease. They never paid rent. How do you ‘love’ somebody and you’re going to flush her down the toilet?”

The Abellos later returned the ashes to Skylar, under an agreement hashed out in housing court, documents show.

Skylar, who is seeking to reinstate her own eviction proceeding against the Abellos, said she has no idea what happened to her parents’ belongings, after seeing social media posts apparently showing the apartment empty of her family’s furniture and mementos.

“A lifetime of belongings, mementos, my dad’s bylines, books, a great vinyl collection” appear to be gone, she said.

“If this could happen to me, it could happen to anybody who retains home health attendants,” she said.

The Abellos and their lawyer declined to comment.

Additional reporting by Georgia Worrell and Helayne Seidman