Here's something that might help.

Here is a link that might be useful: Guidance from bellalino

thanks, the site says it all !! I googled last night and didn't find anything.

I would do his inital on the left, hers on the right, last name in the middle. If you think about how a couple is addressed, it is usually Mr and Ms. Smith, not Ms. and Mr. Smith.

Of course, rules are made to be broken! LOL

Personally, if the towels were for me, I would only do our last initial, perhaps with some scrolling or other decorative embroidery around it.

The traditional way is to choose one person or the other so that your example would be Mary Smith Dixon, which looks like MDS.

Obviously, the man's would read as Lawrence James Dixon, or LDJ.

It is a new thing to use the couple's names together, but if you do so, it would be woman name, last name, man name so would look like mary Dixon Larry, or mDl.

I love monograms! I mix it up...some of our towels have mine, some have his. FWIW, my husband loves it that our MBR pillowcases have his initials on them.

I think if you're not using the bride's name (so retro), then use a single initial. Or something amusing. My towels say
WET and DRY.

I always thought it should be woman's first, shared last name, then man's first so...

MDL

If it is a new thing to use the couple's initials together, then everything old is truly new again. I have my grandparents' glassware and crystal serving pieces etched with their initals in that way. I believe these pieces are from the 1940's or '50's! I love how trends come and go, but I thought that monograms were timeless.

Enjoy your new towels!