Where do I file??

What is the name of your state (only U.S. law)? Arizona

My brother was married and lived in Washington for 11 years. He recently left his wife and moved to Arizona in August 2010 to avoid being harassed by her. He is now ready to file for divorce (with children) but should he file in Washington or Arizona?

WA currently has jurisdiction. If he stays in AZ long enough to establish residency (90 days), he could file in AZ if all he wants is a divorce.

HOWEVER, the state that can determine custody of the children would be the best place to file. That will be the place where the kids are living long enough to establish residency.