Red Sonja, Conan, and Robert E. Howard
Did Robert E. Howard create Red Sonja?
Technically, Roy Thomas is the creator of Red Sonja. Thomas relates the creation of Red Sonja in his afterword for The Chronicles of Conan Volume 4: The Song of Red Sonja and Other Stories: she was inspired by Robert E. Howard’s character Red Sonya — note the spelling — in the historical adventure “The Shadow of the Vulture,” as well as certain elements of Howard’s other redheaded sword-woman, Dark Agnes.
How does Red Sonja relate to Conan?
Ostensibly, Red Sonja and Conan are contemporaries, both sharing the Hyborian Age setting. However, the Red Sonja trademark is owned by a different company than the one who owns the Conan trademark.
So does this mean Rose McGowan can be Marique in Conan the Barbarian (2011) as well as Red Sonja?
Pretty much, yeah.