Backing up very large external drives

I am in the process of consolidating photo files from over a dozen had disk drives that I have taken over the past 60 years. I use Time Machine (TM) on my iMac for backing up my internal 2TB drive. I am now up to a 4TB external hard drive for my photo files plus two back up drives, one at the location of my iMac and another that is kept off-site. From my limited testing I have found that the program "arsync" does a great job of doing a unidirectional merge between my three photo drives. However, if I delete files on my source drive they will not be deleted from my backup drives with arsync's unidirectional merge. I think a script file could be written using rsync (not arsync) to do a folder merge and remove the deleted files on my source drive. ANYBODY HAVE ANY IDEAS?

THANKS