Conceived as a twin-engine retractable landing gear version of the Messenger, the Miles M.65 Gemini flew first on 26th October 1945 and was an immediate success. It was the last Miles aircraft to enter quantity production and in its Gemini Mk 1A initial form was powered by 100 hp Blackburn Cirrus engines, and had non-retractable auxiliary trailing-edge flaps; one Gemini Mk lB was built with retractable flaps. The single Gemini Mk 2 was created by installing 125 hp Continental engines, while production Gemini Mk 3A aircraft had 145 hp de Havilland Gipsy Major 10s. There were several sub-variants with detail differences, but the most powerful version with two 155 hp Blackburn Cirrus Major III engines, a strengthened structure and larger fins and rudders, was deemed sufficiently different to be designated M.75 Aries.
A total of 170 Geminis and two Aries was built, around two-thirds of them being exported, before the company collapsed in 1947, and the type could be considered as Miles' most popular post-war aeroplane.