The singer filed his petition for dissolution of marriage on July 29, only weeks before their 37th anniversary. A hearing is scheduled for Dec. 12.
The couple have two grown children together, Ben and Amber Jean. Young also has a son, Zeke, from a previous relationship.
Pegi served as the inspiration for many of Young's love songs, including "Unknown Legend" and "Such a Woman." A musician herself, Pegi began touring with her husbands in the '90s and even performed alongside him at the 1994 Oscars.
In 1986, Pegi co-founded the nonprofit Bridge School with Young, an institution specializing in children with special needs. The duo last performed together at the Bridge School's annual benefit in 2013 and were slated to duet again at Farm Aid in September, but Pegi's name no longer appears on the lineup.