RONÍS IS CANON IN EVERY UNIVERSE EMMA IS IN BECAUSE HE IS HER DEAD LOVER.
Little explanation-
For example, in Call of Duty, before Emma joined the military, she had met Ronís at the age of 20 when she and him did a musical together (cough cough Phantom of the Opera when he was The Phantom and she was Christine cough cough). Ronís dated Emma and they were really close until he got sick. He did everything he could to stay there to survive but he couldn’t hold on anymore. Before he passed away (and he knew he was dying), he wrote her a letter that said that she needed to move on to find a better guy, one that was like him. Emma was heartbroken and because of all of her trauma and heartbreak, she joined the military. Her father was opposed to the idea but let her do so because he knew that she was trying so hard. Emma joined Task Force when she was 23 and met Ghost, where they slowly grew to falling in love. She confessed to him after he saved her from being kidnapped and because of a concussion, she was on meds in the medical bay and she confessed to him. He liked her at that point. A little while into the relationship she told him about Ronís and Ghost wanted to do everything he could to make Emma happy, like Ronís did. Emma got a promise ring from Ronís before he passed and she continues to wear it. Ghost lets her because he knows how much it means to her. He’s actually alive and well in the Dark Deception universe (and is her third husband). He did pass away when Emma was alive and she met him in purgatory again. That’s how I plan to make the most heartbreaking angst guys!!