wow they sound seriously creepy!!
i would definitely be concerned that they think it's okay to just rock up and take your daughter without your permission.
i think you should talk to your real estate about the situation. if they are renters and rent through the same agents then they may be able to have them kicked out. my sister was having major problems with her neighbour, she complained to her RE agent and the agent had the man removed from the house. she now has new neighbours and no problems!