Kin of a grandmother and grandson killed in a Long Island plane crash are blaming the family’s wealthy patriarch, who also died in the tragedy, for the incident, new court papers show.

The sister and father of the dead grandson, 22-year-old William Maerov, have filed separate wrongful-death suits using the same law firm to target the estimated $150 million estate of late plane owner and builder-to-the-stars Ben Krupinski.

Krupinski was Maerov’s grandfather, as well as grandad to Maerov’s sister and now one of the plaintiffs suing his estate, Charlotte Maerov.

William and Charlotte’s dad, Lance Maerov, also is suing Krupinski’s estate over the crash involving the builder’s Piper PA-31 Navajo. Lance had been married to the siblings’ mom, Krupinski’s daughter, Laura, who died last year.

Charlotte and her father claim that Krupinski — who built luxury mansions for Martha Stewart and Billy Joel — and pilot Jon Dollard knew bout the poor weather conditions that day but flew into the storm anyway. Krupinski also was a pilot.

Charlotte and Lance Maerov also are suing Krupinski’s plane companies, Long Island Airline and East Hampton Airlines, LLC.

Krupinski, 70 — who fell out with his daughter Laura, a former Wilhelmina model, in 2013 when she told her mom Bonnie that Dad had had an affair with Martha Stewart — was killed in the off-shore crash near Indian Wells Beach on June 2, 2018, along with his grandson, Bonnie and Dollard, 47.

Charlotte is the administrator for Bonnie’s estate and suing Krupinski’s holdings on behalf of her late grandmother.

“During the flight, Dollard and [Ben] Krupinski could see a wall of black clouds containing thunderstorms that was directly in the flight path of the Subject Aircraft, and nonetheless continued to and did fly directly into the line and area of multiple convective thunderstorms,” her Manhattan Supreme Court lawsuit alleges.

“Dollard and [Ben] Krupinski knowingly and intentionally flew the Subject Aircraft directly into the most dangerous depicted weather, rather than diverting to a different airport or altering the flight path to the destination airport.’’

Lance Maerov, filed a similar suit against Ben Krupinski’s estate on behalf of his son.

As a result of flying into the storm, both Bonnie, 70, and William suffered emotional distress and fear as they were aware of their “impending” deaths, the two suits say.

The family had been returning from on a flight from Rhode Island to pick Charlotte up from school. She survived after having landed safety in East Hampton on a second private plane, the East Hampton Star reported.

Both suits seek unspecified damages and name Robert White the executor of Ben’s estate.

Lawyers for Lance and Charlotte declined to comment. White did not return a request for comment, nor did the airline companies.