His heart grew weary at the thought . It was a new reaction to a painful memory . Vader wondered if this was how Obi - Wan had felt when they fought on Mustafar . Anakin promptly buried the thought as he took control of the battle ; he did n't really want to know .

Based on the preceding passage, choose your answer for question Who might Obi - Wan be to him ?
Pick your answer from: [I] Subordinate [II] None of the above choices . [III] Friend [IV] Stranger
The answer is:
[III]