The arrests follow raids on a series of premises that were being used to grow cannabis, including a three storey former nightclub in Coventry.
A 19-year-old man has died and a woman is seriously ill in hospital after they are believed to have taken the drug MDMA in Leamington Spa.
Mohammed Shabir and brothers Manjinder, Davinder Singh Thakhar admitted to participating in the activities of an organised crime group.