Child custody

My fiance is divorced with two children (3 and 4 y/o) from his previous marriage. The four year old was 3 months when he met her so is not biologically his but has acted as loco parentis. Child custody for both children are the same in their divorce papers, even though one is not biologically his. They share joint custody where everything is 50/50. He gets them 2 weeks of every month and she does the same. No one pays child support- everything is equal. Recently she told my fiance she is moving out of state, about 12 hours away and is taking the kids with her. Since he is not a biological parent to the oldest, does he have any say about her? So is he is pretty much forced to either let her take both kids and only see them holidays and summers or to split them up?

He could file for custody and ask the court to prevent her from moving his child out of state. The child who isn’t his is a more tricky issue, especially if he hasn’t adopted it.