Another one bites the dust.

Dennis Quaid’s wife, Kimberly Buffington-Quaid has filed for legal separation after 8 years of marriage.

She is asking for joint legal and sole physical custody of their 4-year-old twins but supports the idea of visitation.

Kimberly’s lawyer will also ask for spousal support and attorney fees.

The couple has had a rough year; in March Kimberly filed for divorce but withdrew her petition 2 months later.

A source close to the couple tells TMZ that "Kimberly is fed up with Dennis' cheating and wants out of the marriage." Adding that "He's not a good husband."