Copyright law says the creator owns their work unless they agree to transfer ownership to someone else in writing (if an exclusive transfer), or unless their employer owns their work. So this photographer presumptively owns the photo they take and they only sell copies to their customers, unless there's a written contract that says otherwise.
Both parents of a child don't need to consent, unless there's a custody agreement that limits the mother's right to make decisions for herself and her child.
If your girlfriend didn't read the photographer's contract and realized that he owned the copyright to the photos, or maintained the right to use the photos for promotional purposes, that's why she or you should have hired a lawyer BEFORE signing any contract.
You can try to buy the copyrights and negotiate something with the photographer, but the photographer's got all the cards in this game.
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This is a good example of why you should never sign anything without reading it & asking questions if you do not understand. I would start by asking the photographer to take it down, he may be willing to take it down upon request in order to avoid any litigation and negative publicity.
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Hire a lawyer and have them send a cease and desist letter; the photographer will see you mean business and will likely back down.
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