There is no Robert E. Howard estate, though. Howard apparently has no living heirs. Conan Properties International, a company in no way connected to Howard, his family, or his heirs, bought up the trademarks (and some copyrights, mostly on published versions of stories that were only released after Howard’s death) some years back- they act as if they own all the rights to the character, but the legality is, at best, questionable.