This half-human and half-animal composition has led many writers to treat them as liminal beings, caught between the two natures, embodied in contrasted myths, and as the embodiment of untamed nature, as in their battle with the Lapiths, or conversely as teachers, like Chiron. The centaurs descended from Centaurus, who mated with the Magnesian mares. Centaurus was the son of either Ixion and Nephele (the cloud made in the image of Hera) or of Apollo and Stilbe, daughter of the river god Peneus. In the latter version of the story his twin brother was Lapithus, ancestor of the Lapiths, thus making the two warring peoples cousins.