Brown Pride Soldiers gang killed 17-year-old Antonio Marks of Marysville.

Two brothers who help beat and stab a 17-year-old to death last June near the Sultan City Hall pleaded guilty to second-degree murder.In return for Tuesday's pleas, Snohomish County prosecutors agreed to recommend a 12-year term for 20-year-old Marco Castillo and a 10-year term for 17-year-old Adolfo Castillo of Sultan.Court papers say they were members of the Brown Pride Soldiers gang that killed 17-year-old Antonio Marks of Marysville. Marks was a member of a rival gang, the Southland Villains.The Everett Herald reports another gang member accused of the attack pleaded guilty last month and two others are awaiting trial next year.