Etheridge filed a Petition for Dissolution of Domestic Partnership in a Los Angeles court Friday, People magazine reports. She asked the court to deny Michaels any financial support, sought joint custody of their son and daughter, both 3, and said "irreconcilable differences" were the reason for the breakup.
Etheridge, 49, and Michaels, 35, had been together for about nine years. They went through a commitment ceremony in 2003 and registered as domestic partners two years later, TMZ says.
In 2006, Michaels gave birth to their children, conceived through artificial insemination from an anonymous sperm donor. The couple reportedly planned to marry legally in 2008 but missed the short period when same-sex marriages were possible in California.
After they announced their breakup in April, Michaels said publicly on the Web that the separation was not a friendly one.