We use the script written by léonie
Script: Batch Change the Date and Time to a Fixed Date
You select a group of pictures, and the script will use the date of the first picture to change the date of the subsequent pictures to that first one incremented by one minute each. You can change the 1 minute increment if you like.
You set the date of the first picture by using Image>Adjust Date and Time:

and the Adjust dialog

But I started by using titles. For instance, my father was in the Marines in WWII, joining in time to be wounded on the USS Pennsylvania at Pearl Harbor. So I had put the pictures in an album and moved them around so that they seemed to be in order. Private was before PFC, then Corporal, etc. Then I added titles like 1941, 1942…1955, 1956, etc. Now I could sort by Title, and they looked pretty good.

I used titles rather than the date metadata, because the dates show in the Thumbnail view, and I could change them very quickly.
Then I did the same for my mother. Then I put them together, and again sorted by title. I saw that some of my guesses didn't make sense looking at both of them together, so I re-arranged them so they made more sense, using the titles to keep them straight. Anyway, I kept adding people who would be with one or the other or both, and kept refining the order until I couldn't get any more precise.
Then I took all the 1941s, for instance, set the date of the first one as 1/1/1941, and then used léonie's script to increment by 1 minute. Then I did the same for the 1942s, etc.
I did this with succession of relatives who might appear together, sorting them individually and then together to get more information. I ended up pretty satisfied with the results.