Are there court orders in place? Would you be moving with the father? Look, if there are no orders then I reckon she could move with you, however without consent from the parents, they would be entitled to make an application for recovery orders from the court.
Now as you're not a biological parent, I reckon the courts would be likely to grant the orders.
Now I'm working on two sentences of info from you - There must be a significant back story here that a judge would hear.