Humans (Homo sapiens sapiens) and the two chimpanzee species (Pan paniscus and Pan troglodytes) are more closely related to each other than horses are related to donkeys.
Horses and donkeys are of the same genus, Equus.
If more distantly related species like horses and donkeys form a single genus, so too do more closely related species like humans and chimps.
This means that all extinct species that share a common ancestor with humans and chimps, including Australopithecines, also belong to the genus that includes humans and chimps.
Genera and species are biological categories, and biological categories are defined on biological criteria only. The allocation of humans and chimps to different genera derives from the mythological tradition of the West — the three Abrahamic traditions that actually go back to Zoroaster of Persia — which separates humans from the rest of Nature, which it sees as 'fallen'.