Bryan Packer is a good son:
I have been helping my parents migrate all of their files over from a 10-year-old iMac to a new one. They have two iPhoto Libraries that I copied over to the new iMac. Now, on the new iMac, there are three Photos Libraries. I have no idea how the extra libraries came about. Is there a way to merge the iPhoto Libraries and the Photos Libraries so we can see all of them together in one library in Photos?
This seems to be a multiplication problem. Each iPhoto Library, when opened in Photos, becomes a Photos library. So on launching Photos with the Option key held down, you should see both old iPhoto libraries and both new Photos libraries. The third Photos library may have been created during setting up the Mac, and contains no images, although you can select it using the Option key launch sequence to make sure.
Unfortunately, Apple’s greatest missing piece in iPhoto and Photos is the ability to move photos and albums among libraries and to merge them. For that, I routinely recommend the only third-party option out there, PowerPhotos, which costs $30 for a bundle of itself and the developer’s previous tool, iPhoto Library Manager. (You can see our review of PowerPhotos 1.1; it’s now at version 1.2.2.)
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