The suspects reportedly also are tied to a killing in Shoreline last fall, according to police records.
The Snohomish attack happened July 23. Police say the suspects may have been seeking revenge in a dispute, and they mistook the brothers for their rivals.
The brothers didn't know the suspects, and they aren't connected to any criminal activity, according to the police chief.
The brothers, 22 and 23, were seriously injured. They were hit with a tire iron and a metal baton, and were slashed and stabbed with knives. One had a collapsed lung. A third brother, 13, escaped the attack uninjured.
Neighbors said the brothers often played Frisbee and football in the field on summer nights.
On Friday, Snohomish County deputy prosecutor Chris Dickinson charged Rachel Rose Marie Patterson, 27, with first-degree assault and second-degree assault. She has no known criminal history. In charging papers, the prosecutor called the attack "unprovoked, random and violent."
Also charged was Tristan Daniel Smith, 28. Smith has felony convictions in King County for rendering criminal assistance and for theft. He also has two misdemeanors as an adult.
The pair are linked to a Shoreline killing, police say, but they aren't providing details.
The killing there was reported Sept. 27, 2012, said Sgt. Cindi West, spokeswoman for the King County Sheriff's Office. Police were called for reports of a fight and found a man dead from a gunshot wound.
Investigators aren't discussing the ongoing case, and haven't publicly named any suspects, West said. Arrest paperwork in the Snohomish attack said Patterson has a pending second-degree murder case against her and that Smith is suspected of rendering criminal assistance. No King County charges have been filed.
Since their arrests, both suspects have been held at the Snohomish County Jail on $100,000 bail.
Police reportedly found bloody clothes and knives from the attack at the couple's home and in the woman's car.
Rikki King: 425-339-3449; firstname.lastname@example.org
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