The Flores brothers rose from street-level Chicago drug dealers to the top of the cartel world, making millions along the way by literally supplying tons of narcotics to cities across the U.S.

That’s according to federal prosecutors, who on Wednesday sought leniency for Pedro and Margarito Flores, who will be sentenced later this month. The feds requested prison terms of 10 to 16 years for the twins — at the low end of sentencing guidelines.

The reason, the feds say, is the brothers’ “unparalleled” cooperation, which led to the downfall of 54 drug traffickers and helped the U.S. build its case against Sinaloa cartel jefe, Joaquin “El Chapo” Guzman.

“The Flores brothers (and their families) will live the rest of their lives in danger,” the feds wrote in a sentencing memorandum. “The barbarism of the cartels is legend, with a special place reserved for those who cooperate.”

Starting in 2005, the brothers for three years ran a Chicago-based narcotics hub, distributing “incomprehensible” amounts of cocaine for both the Sinaloa cartel and their rival Beltran Leyva Organization, the feds say.

The brothers received as much as 2,000 kilos of cocaine for distribution a month. At the same time, they laundered more than $1 billion in drug profits and smuggled an estimated $1.5 billion back to Mexico, according to the memorandum.

The brothers’ reign came to an end in 2008, when they agreed to cooperate with federal prosecutors. In November of that year, they recorded drug negotiations with high-level kingpins in Mexico, where they had relocated. Among them was Guzman, who was caught negotiating a 20-kilo heroin shipment to Chicago, the memorandum states. The brothers have been in protective custody since then.

But while prosecutors recommend minimal sentences, the relationship between investigators and the brothers was at times strained.

At one point during the investigation, the brothers had an associate collect several million in cash from a customer near Washington, D.C. They tried to keep that secret from authorities, the memorandum states. Eventually, the brothers surrendered the bulk of the cash, minus $300,000 for their families and legal expenses. Then there was a 276-kilo cocaine shipment, distributed across Chicago, that they unsuccessfully hid from the feds.

Prosecutors say they were also troubled by two murders tied to the brothers, including one in Chicago. Ultimately, investigators were unable to find corroborating evidence.

Placing the brothers in the pantheon of other local criminal legends, prosecutors say the the Flores twins were likely “the most significant drug traffickers in Chicago’s history.”

“The Flores brothers are in a way the ultimate success story from the criminal perspective,” the memorandum states. “From the point of view of an aspiring drug trafficker, this success would be something to emulate.”