Duchess of Kent's birth name is Katharine Lucy Mary Worsley.
Duchess of Marlborough's birth name is Consuelo Vanderbilt.
Duchess of Windsor's birth name is Bessie Wallis Warfield.
Duchess of Gloucester's birth name is Birgitte Eva Henriksen.
Bubby Kent's birth name is Tajinder Kent.
Kate Kent's birth name is Catherine Kent.
The term 'Duchess of Kent' is a proper noun, the name of a specific title for a specific person. Proper nouns are always capitalized.
Kent Gilbert's birth name is Gilbert, Kent Sidney.
Kent Bottenfield's birth name is Kent Dennis Bottenfield.
Kent MacKenzie's birth name is Kent Robert MacKenzie.
Kent Johnston's birth name is Allen Kent Johnston.
Nicole Kent's birth name is Nicole Shena Kent.
Rolfe Kent's birth name is Rolfe R. Kent.