Unwanted multiple copies of the same photo in 'Photos' of a iPhone 11.

How are you sharing your photos with your wife?

If you are sharing an iCloud/Apple ID - then you also need to worry about her phone and mac settings. Because anything that causes a change between her phone and mac will also be replicated back into iCloud at her end, and then will replicate onto your phone/mac also. It is generally not advised to share apple IDs.

In order to work out what is going on, you will need to look at specific examples of duplicated photos - work out what is different between two two of them by looking at the info for both files - is it filename, type, metadata etc - also compare with the original version of that file on the source (whether it is the phone or a camera and whether the original import location is your phone or mac.)

And if either of you use both USB and iCloud to sync photos that is likely to cause duplication, since the file date of the file transferred via iCloud will be different from that on the phone so will appear as a different file.

And this can cause multiple duplicates - eg

File transferred via icloud has a different date from the one on the phone. So when synced via USB is duplicated.

Then the duplicated version is transferred back to the phone via iCloud - with the different date - to be copied again next time.

Hi

This problem normally comes when the files are changed in some way as they are transferred to the Mac. Often the result of using different methods of transferring the files (EG texting / direct connection / photostream / iCloud). Pick one method of transfer from phone to Mac, and stick with it. Don't mix them.

Different versions of IOS can also impact this EG when photos are converted from HEIC to JPG. Iphone setting photos>transfer to mac or pc - set to automatic might convert the files. Try setting this to "keep originals". The phone will then send the files in the original HEIC format instead of JPG. (This is the most likely cause, and the easiest one to check for). However you'll still have duplicates on your mac in jpg format which you could choose to delete from the imports folder (if you are sure you still have the originals on your phone)

Another cause can be when iCloud photos is enabled on the phone with “Optimise phone storage” set. If iCloud re-downloads an image that has been optimised, that can result in it being seen as a new image. Even worse, any photo uploaded from your mac to iCloud, then downloaded to the phone with iCloud can be seen as a new image when synced via USB. Best solution; DON’T mix iCloud sync with USB sync.

Photostream is also being phased out, and hasn't been improved for some time resulting in an inability to work with some file types.

Images will only be recognised as the same image if the file being compared on your mac is exactly the same as the one on your phone. Same file name and type, same size, same metadata etc. Often images imported from other apps (whatsapp, messenger etc) can also be changed during transfer.

By far the easiest way to manage photos is by using iCloud sync, but that does have a monthly cost.

What version of MacOS do you have?

What version of IOS is on you phones?

How are you syncing the photos between your iPhone and Mac? By iCloud Photos, My Photo Stream or cable?

Could they be "bursts" photos?