"It is great news for everyone that the will contest has settled without a trial," grandson Philip Marshall wrote in a text message.
The settlement, ratified in Westchester County Surrogate's Court, details how Astor's estimated $100 million estate will be distributed and cuts from about $31 million to $14.5 million the inheritance of her only child, Anthony D. Marshall, who was convicted of stealing from Astor in her later years.
Astor died in 2007 at age 105.
Philip Marshall, who was the first to publicly accuse his father, Anthony, of mishandling Astor's affairs, said the office of Attorney General Eric T. Schneiderman "has done a great job representing the unnamed charities who are beneficiaries," The New York Times reported.
The settlement takes away from Anthony Marshall and his wife Charlene control over which charities would receive tens of millions of dollars from the estate, the Times said.
The settlement is based on a 2002 will and voids changes in 2003 and 2004 that gave her son more control over her estate and reduced the amount of money for New York universities, libraries, parks and museums.
Astor's son and Francis X. Morrissey Jr., a lawyer who did estate planning for her, were convicted of defrauding her and stealing from her. Each was sentenced to one to three years in prison. They remain free pending appeal.