How do I merge the files of two formerly single clients who married in 2019?

[IRonMaN]

Unless you do magic acts on the side, you can't.  Keep the client with the most stuff and delete the other file.

[JEromanix]

Great Answer! 

I am an eternal optimist, I was sure that you could to do this 😞

[IRonMaN]

But we need more optimists ------------------------- we have too many pessimists around here.  Keep filling that glass half full! 😀