Just a quick little drabble here. Please enjoy. I do not own Fullmetal Alchemist, and this is pure interpretation on my behalf.
Some people considered it unromantic. Others said she was selfish. Keeping your maiden name after marriage was something not commonly done in Amestris; they believed that once a woman was married, she left her own family and legally became her husband's property, for lack of a better term.
When Riza Hawkeye had married Roy Mustang, everyone had expected her to change her family name, thus becoming his wife in every aspect. When she had declined, albeit politely, she had been somewhat criticized by both their families, by friends, even military personnel who knew them by nothing but rank commented on this choice. Why, after all of these years of following him, staying loyal to his every motive, and practically being married in every sense except for the lack of a few sheets of paper bearing their signatures, had she chosen to decline the chance to be his wife in what the people considered every sense?
The answer was simple; he had always called her Hawkeye. He had never called her by her first name, unless it was immediately suffixed by her last, and she was content that way. She had done, and could do so much morr for him as Riza Hawkeye as opposed to Riza Mustang. As Riza Hawkeye, she was his loyal confidante, his dedicated bodyguard, and his trusted subordinate. As Riza Mustang, she seemed less than herself; like the formal occasion accessories most of their superior officers liked to call their wives.
Even now, years after their wedding (and it was quite sad to say that they both forgot their anniversary every year with unfailing consistency), he still woke her in the morning with her rank and last name, a smirk playing on his lips, his breath a welcome, soft warmth against the shell of her ear.
Roy knew that her loyalty lay with him in every way he could think of (and probably plenty that he couldn't ponder in a single lifetime). Riza needed no material evidence to prove that she would walk beside him the whole way, as a separate but close set of footprints beside his on the road of life. And one day, near the end of his life, he would undoubtedly look back, see the low points in his life where there was only one set of footprints, and then realized those were the points at which she carried him.
END
To guard my own plagiarism morals, the last few lines are actually based off a short religious story by an unknown writer. But I thought that it suited this quite well! Thank you for reading.