How old do kids need to be before they can say they don't want to see other parent

Short version -- you change the order by way of a motion.  Not enough information provided to be more specific -- it makes a difference WHERE the underlying order was entered, and who has been where since then.  For background, see "The Basics of Family Law Jurisdiction" posted at http://willicklawgroup.com/child-custody-and-visitation/. If jurisdiction is in Nevada, there are at least two obvious means of proceeding, based on the non-support (an old case called Chesler may be of use) and based on the age of the children and the concept of "teen-age discretion" (they are a bit young for this, but it is worth discussing). If you are not sure which state has jurisdiction to make a decision based on your facts, get the underlying order, and a timeline/chronology of who has lived where since it was entered, and call this office, or that of another family law specialist well versed in jurisdiction, and it can be figured out in short order; you will then know what you can do, and where you can do it.