My older half sister was kidnapped repeatedly by her bio parents.

Legal custody seemed to be whomever had the kid in whichever state at any given time.

One episode ended when her bio dad showed up at air port with a shotgun and bio-mom had convinced the out of state police to be on her side. After a night in jail anyway. Police made the bio-dad go home.

My mom tailed her at school for a few years. Stopping another attempt before it ended.

Was messed up every way possible.