Police say the 46-year-old's driver, Carlos Trujillo, and his cousin, Leonard Trujillo, have been arrested.
Carlos Trujillo pleaded not guilty to conspiracy to commit murder in Stamford Superior Court this afternoon and says he didn't kill Kissel.
Leonard Trujillo appeared Mondy morning in Worcester District Court in Massachusetts, where he signed paperwork agreeing to return to Connecticut to face charges of murder and conspiracy to commit murder.
He is being held without bond and will return to court Tuesday so Connecticut authorities can pick him up.
The arrest warrants are sealed.
At a press conference Monday, Greenwich police would not comment on a motive for the crime or say whether there would be more arrests.
"This case is not over," said Greenwich Police Chief David Ridberg. "The investigation remains open. We still have more work to do on it."
He said officers from several states and federal agencies did hundreds of interviews in the case.
Among the theories that officers investigated, he said, was that Kissel's death was a suicide-for-hire. But he said research showed that such killings are extremely rare.
"If it ends up being the case, that's fine," he said. "If it doesn't end up being the case, that's fine too."
Carlos Trujillo, the last person to see Kissel alive, had been interviewed by police several times and had given them samples of his DNA, fingerprints and some personal documents, his attorney has said. He has denied any involvement in Kissel's death.
Kissel's brother, Robert, was a wealthy banker whose wife was convicted of murder in Hong Kong in September 2005 and sentenced to life in prison after feeding him a milkshake laced with drugs and then beating him to death in November 2003.
Andrew Kissel and his estranged wife, Hayley, had cared for Robert Kissel's three children until they were handed over to the custody of a relative, who lived near Seattle. Andrew and Hayley Kissel had two children of their own.
The couple's divorce was heating up before he was killed, court records show. In divorce papers, Hayley Kissel had accused her husband of being a belligerent alcoholic.
Kissel's criminal cases were pending in federal and state courts in New York at the time of his death. The federal case charged him with real estate fraud and state prosecutors charged him with grand larceny, alleging he stole nearly $4 million from his Manhattan apartment cooperative.
Kissel also was being sued by a former business partner.
