Syed Raheel Farook home
A California police cruiser stops outside the Corona home earlier this year of Raheel Farook, brother of San Bernardino shooter Syed Rizwan Farook.Reuters/Alex Gallardo

The older brother of Syed Rizwan Farook, the man who killed 14 people in a terror shooting rampage with his wife at a holiday party in Southern California, has been arrested and charged with marriage fraud, conspiracy and lying under oath. Syed Raheel Farook was taken into custody along with his wife, Tatiana, and her sister, who were charged with the same crimes, reported the Washington Post.

The charges are not linked to the 2015 attack by Rizwan Farook and his wife, Tashfeen Malik. But the investigation into the shootings inspired by Isis uncovered marriage irregularities linked to the killer couple's neighbor, officials said.

Neighbor Enrique Marquez, was allegedly paid $200 (£137) a month to pretend to be legitimately marriage to Tatiana's sister, Mariya Chernykh, 26, reports the Press-Enterprise. The two did not live together.

Raheel Farook, a decorated Navy veteran, and his wife allegedly lied to officials and falsified documents to help maintain the ruse so that Chernykh could illegally gain US immigration benefits. Both Tatiana Farook and Chernykh are Russian immigrants.

Chernykh faces additional charges of perjury and fraud. She could be sent to prison for up to 25 years if convicted of all the charges against her, reports the Post. All three have pleaded not guilty to the charges.

Though the alleged marriage fraud isn't linked to violence, the crack down on the scheme sends a strong message of potential penalties to anyone who associates with terrorists. "Today's arrests open a new phase in the process of bringing to justice all individuals who allegedly committed crimes that were uncovered during our exhaustive investigation," US Attorney Eileen Decker said in a statement.

"We made a solemn commitment to the people of San Bernardino that we will turn over every stone to identify those involved or engaged in some form of criminal activity related" related to the shootings, and "the indictments today reflect the work we've been doing to honor that commitment," Decker told the Press Enterprise.

Enrique Marquez was already being held on charges of conspiring to carry out earlier attacks with his neighbors planned for 2012 that never came to be. He has also been accused of purchasing the two assault rifles used in the San Bernardino shootings, and now faces the sham marriage charges.