Severide calls her "Royce" at first, because the name "Renée" reminds him of his cheating ex-fiancée, Renée Whaley.
Kelly and Renée's relationship ends prematurely as she has to move to Madrid, Spain, for a promotion. Kelly initially considers going with her, but his father helps him realize that he would never be happy if he gives up his career as a firefighter, so he prefers to break up with Renée.
A few months later, Renée comes back from Spain and reveals to Kelly that she is pregnant with his child.
Renée moves in with Kelly and they get ready to raise the baby together. However, Leslie Shay believes that Renée's due date is not consistent with the last time she and Kelly slept together before she left for Spain. She shares her concerns with Kelly, who starts having doubts. He asks for a paternity test, which reveals that the baby is indeed not his, but rather the result of a one night stand Renée had a few weeks after arriving in Madrid.
Renée is devastated, because she had genuinely believed and wanted the baby to be Kelly's. She and Kelly then break up for good.