Immortality

Amara and Eric have been inseparable since they first laid eyes on each other. Eric is three years older than Amara. Eric and Amara are siblings and fairies and heirs to the throne of the Fairy Realm. They were both cursed when they were three and a few months old. They can't reproduce. But a horrible side affect was immortality. They found out about the curse when they were twenty-one and eighteen. Fearing their fate they fled to the Humanoid Realm. They were followed. By who?