Orphaned in childhood, Evangeline Mittermeyer was sent to live with distant relatives, the Mittermeyer family. Growing up alongside Wolfgang Mittermeyer, their close relationship blossomed into romantic love. Wolfgang proposed to her on his Imperial Academy graduation day, and they married.

Despite years of unsuccessful attempts to conceive a biological child, Evangeline and Wolfgang's devotion to each other remained undiminished. Their deep mutual affection and strong bond made them widely regarded as an ideal couple.

Following the death of Wolfgang's close friend Oskar von Reuenthal, Evangeline and Wolfgang adopted Reuenthal's infant son, Felix. They raised Felix as their own child, providing him with a stable home life.

Evangeline served as a stabilizing and supportive presence for Wolfgang, especially during political and military upheaval. She traveled to Phezzan to reunite with him after a long separation, demonstrating her commitment to their family despite his military duties. During this reunion, they discussed personal matters, including Wolfgang's concerns about Kaiser Reinhard von Lohengramm's personal life, though Evangeline maintained her distance from politics.

Her role centered on her relationship with Wolfgang and their family. She provided crucial emotional support during Wolfgang's distress over Reuenthal's rebellion and its consequences, grounding him amid professional turmoil. Her presence highlighted the contrast between Wolfgang's stable domestic life and Reuenthal's turbulent relationships.