The term 'Sweet Potato Cousin' refers to two root vegetables, the YAM and the OCA. The YAM is a starchy, sweet-tasting root vegetable that is native to Africa and Asia. It is often used in soups, stews, and curries. The OCA is a tuberous root vegetable native to South America. It has a slightly sour taste and is often boiled or roasted. Both the YAM and the OCA are cousins of the sweet potato and are used in many dishes around the world.