A story in the Religious Revelations Universe
Pagan priestess promotes insemination as a high sacrament to be administered joyfully and often. Spirituality and sex start with the same letter for a reason.
While on a camping trip with his sister and his Grandpa Andy saves what seems to be a young girl from being raped. Due to a misunderstanding, his reward is being turned into his younger sister's twin.
His disease was emotional. Hers was in her pancreas. Algebra brought them together. The earth tried to eat her. Then he learned to eat her, and they lived in their sex palace. There's a fairy godmother, Bluetooth, and auto financing. Excess happy tears. And a medical breakthrough. Also, horses.