The McMichaels and Bryan are already serving life sentences in Georgia after being convicted of murder in a state court last fall.
All three were previously convicted of murder in a Georgia state court and sentenced to life in prison for the fatal shooting.
Arbery's parents denounced the deal as a betrayal, and called on the judge to reject it.
A jury convicted all three men of murder, aggravated assault, false imprisonment and attempted false imprisonment in November.
64-year-old Greg McMichael and 34-year-old Travis McMichael were charged last month with felony murder and aggravated assault.
Georgia’s attorney general has asked the U.S. Department of Justice to investigate the handling of the killing of Ahmaud Arbery.
The Justice Department has announced federal hate crime charges in the death of a Georgia man who was killed while out for a run last year.