He didn't. For a long time, he went by the name "Sarge" but he used fake names for his IDs. He used the name "Ember" for his female form and "Johnny" for male. Shortly after we started dating, he wanted to find out more about his past and discovered his memories were altered. He looked at a few of these real memories, mainly his birth, to find out his real gender and name. When he found out, he told me that one of the names he used for his IDs just came to him while he had to think for a while for the other one. That's when we learned he was really born male.
But we didn't learn his last name at the time, only a few months later when we asked the queen.