My Scheming Sickly Husband

Daughter of a concubine. The Heir Apparent of The Ducal Manor is a chronically ill man, offering generous betrothal gifts. I figured marrying a sick man was better than becoming a concubine. I'd wait for him to die and live as a widow. But when other sons tried to seize the inheritance, my supposedly bedridden husband suddenly rose to overcome every challenge. "Rest assured, my lady. I won't let you become a widow." Me??? What happened to him not having long to live?