GOOGLE: April 1963 Popular Mechanics
If you are the least bit curious about how someone built a very nice tandem from two cruiser bicycles, a
men's frame for the front, and a women's step-through for the rear portion.
I think you might enjoy reading and seeing this detailed HOW TO article from long ago.
('BICYCLE BUILT FOR TWO'-by Manly Banister....see pages 176-179 and page 212 in APRIL 1963 POPULAR MECHANICS)