You're right that the photograph is copyrighted and the copyright belongs to the photographer. Whoever bought the photograph portrait just owns just that copy. I don't see how you can stop your daughter's dad from making these illegal copies if he got the negative - how did he get the negative, anyway? Anyway, you and your daughter aren't responsible for anyone else's infringing activities. If he gave you an illegal copy, I guess you could offer to pay the photogragher something.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.
What, do professional photographers still use film and generate negatives? Well, I guess you can still get Kodacolor these days, but I've heard that Kodak has taken my Kodachrome away (which would have generated a color transparency positive).
Anyway, it doesn't so much matter whether the copy is made from the negative or from the positive print, either way, it's making a copy, which is one of the exclusive rights of the owner of the copyright to the image.
Generally, when an independent photographer (not an employee) makes an image, he owns the copyright to the image and has the power to prevent others from making copies of the image, or he can grant permission to do so, either generally or with certain restrictions. As you will see from the court decision in Marco v. Accent Publishing (in which I participated on behalf of Mr. Marco), a photographer was held to have the power to grant permission to a magazine to publish photos for editorial use but to prevent their reuse in advertisements without a separate payment.
The appropriate thing would be for the father to seek to acquire from the photographer permission to make copies of the original. The photographer would typically ask for further compensation for this, or he might simply decline and assert that he wants to control the final look of each copy. In either event, the photographer would be within his rights.
Gerry's refreshing levity and Pamela's spot on answer are the only answers you need.
I write to note only that what your daughter's father would be doing is copyright infringement -- which, in the vast majority of cases, is a civil wrong which is NOT "illegal" in the sense that the conduct violates any criminal statute. In short, no law enforcement agency would have any authority to take any action against him if he copied the photographs. He would not be committing a crime.
While some copyright infringements are crimes, they are only criminal when the damages caused by the infringement are in the many thousands of dollars.
The consequence of your daughter's father making infringing copies of the photographs is that the photographer could sue him and seek monetary "damages." The photographer would win that lawsuit.
The photographer, however, would be very reluctant to file suit because it could not be filed until the copyright in the photographs was first registered with the Copyright Office (a 4 month wait unless expedited) and the cost of suit would likely outweigh the damages that would be awarded -- not to mention that the lawsuit would disrupt the photographer's business and take his or her time away from real world life.
The reality is that there is very little that can be done when only a few infringing copies of a copyrighted work are made. The benefit of enforcing the copyright in those situations is more than offset by the cost of the enforcement. It is, in those situations, our inherent sense of right and wrong that controls whether we succumb to the enticement of grabbing something for nothing.