Many facts are missing from your narrative. You do not say whether there was a prior court order anywhere as to custody of these children, which makes a big difference as to whether we are dealing with "original" or "modification" jurisdiction.
If 6 months have passed since the kids and parents moved to Nevada, that is now their "Home State" and the only place where an action relating to custody or visitation of those children may be filed. Until that point is reached, their prior State (apparently Oregon) is the place where a custody action could be filed under the UCCJEA. And if any party to the prior custody order (if there was one) remains in the State that issued it, that place remains the State with modification jurisdiction.
These rules are discussed in the article "The Basics of Family Law Jurisdiction" that is posted on the Child Custody page of our firm website:
http://willicklawgroup.com/child-custody-and-visitation/. You should consult with a family law specialist.
In the meantime, if you are concerned with the physical health and safety of the children, you can call the police and ask that child protective services do a health and safety check.
Answered on Feb 21st, 2014 at 10:32 AM