Andrew Quinn, 31, James Quinn, 26, and James Swankie, 31, were in the dock during a private hearing at Glasgow Sheriff Court.
Andrew Quinn, of Glasgow, is accused of one charge of conspiracy with as well as a separate charge of attempted conspiracy.
James Quinn, of Glasgow, meantime faces two charges of conspiracy while Swankie is alleged to have committed one conspiracy.
Also linked to the probe were Andrew Robertson, 52, William Quinn, 57, and 26-year-old Regan McKay.
Robertson, of Wishaw, Lanarkshire, faces a charge of being involved in serious organised crime.
William Quinn, of Glasgow, is accused of acquiring criminal property and possession of criminal property as well as possession of drugs.
McKay, of Glasgow, meantime faces a charge of being concerned in the supply of a controlled drug.
All six men made no plea at their respective hearings to the charges they face and were committed for further examination.
Andrew Quinn, James Quinn and Swankie were remanded in custody.
They will appear in court again within the next eight days.
Robertson, William Quinn and McKay were granted bail with their next court appearances to be determined.
