The Demon King's Contractual Partner is the Real Princess

Switched at birth, her magic sealed, Emily grows up a servant. She saves the wounded Demon King one night—and conceives his twins. Framed and banished, she returns three years later with her magical children, bound to the ruthless king by a contract. He doesn't know she's the true princess or that the twins are his. As war erupts and her magic awakens, Emily must unmask the fake princess, reclaim her throne, and decide if the man who cast her out deserves a second chance.