Prosecutors in Chicago are recommending a lenient prison term of between 10 and 16 years for two drug cartel associates-turned-witnesses whose father is thought to have been killed in retribution.

A filing Wednesday in Chicago federal court announced a Jan. 27 sentencing date for twin brothers Pedro and Margarito Flores.

Their testimony led to indictments in a billion-dollar trafficking conspiracy of key Sinaloa drug cartel figures, including drug lord Joaquin 'El Chapo' Guzman.

Prosecutors say the twins' drug network once extended from Chicago to New York and Los Angeles.

They pleaded guilty to conspiracy and faced a life sentence. In arguing for leniency, prosecutors note the brothers' father was "presumed killed" in Mexico because of their cooperation.

Mexican authorities captured Guzman last year but haven't said if he'll be extradited.