Managing multiple Photo libraries

How to merge libraries will depend on the work you invested into the Photos Libraries.

Have you added adjustments to your photos or keywords? Did you create albums and folders to structure your Photos Library?

• In Photos 7 or later (macOS 12 or later) you can import photos from one library into another library. But that will just import the photos or videos, with the adjustments applied, the albums and folders and keywords will be missing. YOu will just import selected photos, not the structure of the library. But the big advantage by importing directly from the otherlibraries will be, that you canimport the edited photos paired with the original version as an entity, just one photo, so you will be able to revert the adjustments individually or revert to the original. But the structure of your library will be lost. And you cannot import from an iCloud Photos Library, onlyfrom local libraries.
• In older versions of Photos you would have to export the photos from one library and import them into the other library and would have to export the originals and edited versions separately.
• To merge the libraries including the structure (albums, folders, keywords) you could upload all libraries to iCloud Photos, one after the other. The iCloud syncing will merge the structure and solve conflicts between duplicates. This will give the best merge, but requires plenty of cloud storage and a lot of patience. It will take several weeks for large libraries.
• PowerPhotos, as recommended by Yer_Man, will be a lot faster than merging in iCloud, and on macOS Ventura it can also merge selected albums from an iCloud Photos Libray into another library.

You don't mention which version of Photos you have.

If you have the current version then you can import from one library to another, or, with any version, you can merge libraries with PowerPhotos:

https://www.fatcatsoftware.com/powerphotos/

I have a Xr 11 iPhone

Thanks for sharing, but the relevance to inquiry or the responses is not clear.

Again, the relevance to inquiry or the responses is not clear. Perhaps you should create your own thread and pose your query rather than cluttering up someone else's.