Whilst Prince Harry's has been known for many years now, Meghan's individual monogram conforms to the same design with a Coronet of her rank as the wife of a child of the Heir Apparent and her initial is in the same font as her husband's (and, coincidentally, the same as TRH The Duke and Duchess of Cambridge).
The novelty is their combined Cypher. Taking advantage of the fact the the letters H and M are very similar, their combined monogram marries the two initials into one, simple, symbiotic whole which is very pleasing to the eye.
Whilst not exactly heraldry, I thought I would include this snippet as I have shown the Scandinavian Royal Cyphers previously. An interesting Summer diversion...