Doctor Brown was a male Human scientist who lived during the 23rd century. During the 2260s, he was an assistant to Dr. Roger Korby and friend to Christine Chapel; her affectionate name for him was "Brownie".
Sometime after arriving on Exo III in 2261, both Brown and Korby perished on the planet. With Ruk's help and with the records Korby could find, they were able to construct an android copy of Brown. (TOS: "What Are Little Girls Made Of?")