There are 3 different types of Kybrothilians: Progenic, Scythe-eared and Protean.
The Progenic Kybrothilians are more biologically composed than Scythe-eared Kybrothilians. This makes them less prone to become sick when coming close to Anarchium veins. They cannot produce Anarchium-rich milk like the Scythe-eared Kybrothilians.
The Scythe-eared Kybrothilians are less complex, but more powerful. The maternal Scythe-eared Kybrothilians are the most important species because of their ability to produce Anarchium-rich milk, which is a great advantage for a species that lives on a planet with no food (plants/animals).
Another ability for the Maternal Scythe-eared Kybrothilians is their 3rd hand, which is used for more rough tasks (such as fending off enemies) that their "gentle" hands cannot handle. Their gentle hands are mostly used for taking care of their young and carrying their big bosoms, which produce food for themselves and other relatives.