Canadian real estate developer Adam Anhang was the target of a $3 million plot in which wife Aurea Vazquez Rijos tried to kill him, according to reports.
Vazquez was arrested Sunday by police in Spain after being sought for five years in the alleged murder-for-hire scheme in Puerto Rico, the FBI confirms.
The Puerto Rican suspect was taken into custody as she got a flight from Italy, where she has lived for years and gave birth to another man's twins.
A U.S. grand jury charged Vazquez in 2008 with offering a man $3 million to kill her husband, and she has evaded attempts to bring her in since.
She denied the charges but refused to cooperate with police and fled Puerto Rico for Italy, where she lived in Florence and, more recently, Venice.
Abe Anhang, the victim's father, on Sunday said authorities told him that Vazquez's sister and her former husband have also been charged and arrested.
"We're hopeful that after such a long time that justice will be done," Abe Anhang said. "It's been almost five years since she's been a fugitive in Italy."
After Anhang's murder, Vazquez refused to cooperate and filed suit against her late husband's family, seeking $1 million in damages and millions more from his estate.
A judge in Puerto Rico dismissed her suit.
Anhang, 32, was beaten and stabbed to death in a popular tourist district of the Puerto Rican capital in September 2005 as he walked with Vazquez.
He was killed as the couple walked from a restaurant he had bought for her in historic Old San Juan, where they discussed their pending divorce.
She sustained minor injuries in the attack.
A wrongfully convicted Puerto Rican man spent eight months in prison for the high-profile slaying of Anhang before getting released in 2008.
At that point, Alex Pabon Colon was indicted for the murder.
Since then, the FBI has been working to arrest Vazquez but ran into difficulties because Italy does not extradite suspects who face the death penalty.
According to the 2008 indictment against her, Vazquez offered Pabon money and lured Anhang to the tourist district the night of his death.
The indictment said two other unidentified people were also involved.
Anhang developed beachfront condominiums and hotels in Puerto Rico and also was CEO of an online gambling software company based in Costa Rica.
He had moved to Puerto Rico a year before the attack.