You should first send her a DMCA take down letter if you own the photo. If she took it, she owns it. However, especially when it comes to minors, and adults for that matter, when persons use photos online or publication they still need explicit permission. Otherwise they can be exposed to liability. Because the photos are of minors, there are even more stringent controls over this. I would recommend sending a letter to the Facebook to take the photos down, given their Terms of Service.
Complaint to Facebook first, demand letter second, then lawsuit if you are really committed to having them taken down. You will need to see a lawyer in your area.
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It depends. Generally people own the copyright to the photos they took. If the brother's ex GF took this photo, then she owns it.
Because kids are too young to consent to use of their likeness, one of their parents has to consent --did that happen here, did her father consent to this use of her likeness?
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