There is no kidnapping. At the worse there may be contempt of court order. But as a friend of the 15 Y/O there is nothing you can do as you have no legal standing in a custody dispute. I recommend you talk to the custodial parent and have that parent begin proceedings. There are non profit organizations that specialize in visitation over stay violations.
Missouri has that law at RSMO 565.156 §5, but in over 20 years, not prosecutor has enforced it. See related link on what to do.
kidnapping They were not convicted of kidnapping because it was a racial subject that they had to face
Murder and kidnapping
The child does not have the right on Missouri. At this point the child is considered a runaway, so you file charges.
If you're in the US... First, there is no 'them' obtaining visitation. It's 'him' obtaining the visitation. The wife doesn't have a right to visitation, but the father does. Second, *you* don't have to give him anything, but the court can order it. Third, the fact that she is facing criminal charges (and you didn't say what kind of charges) does not automatically exclude him from visitation, although the court may place restrictions on his visitation--ie that it be supervised or that the wife not be allowed around the child during his visitation.
Kidnapping is a crime in most countries. In which case "a person" can not drop charges, the charges are made by the state/police (on the basis of a complaint or evidence) and it is up to them whether or not to prosecute the person charged.
Kidnapping charges can be brought against anyone who does not have legal or physical custody of that person. Grandparent, parent, second cousin twice-removed, does not matter.
If the charges are violent felony charges or felony drug charges you will more than likely be extradited to Missouri. If they are not felony charges there is almost no chance that Montana will do anything. Missouri must first file charges against you and then file a warrant for your arrest. Montana cannot file charges for something that happened in Missouri. They can only turn you over to the Missouri State Police to face charges there. I don't really know what "pick up charges on you" means, but you have to see a judge where the crime happened. You can be charged in Montana for something that happened in Missouri.
That will depend on the specific charges. Chances are that it will be ruled to have no limitation.
Time limitations for filing forgery charges in Indiana?
Can the father of my kids take them and move out of state without me knowing? Also can he get kidnapping charges on him for doing that even though he cant support them and he isn't responsible?
Felony charges in one state are viewed to be felony charges in any other state or US possession.