Bonobos are "pygmy chimpanzees" (pan paniscus) - either a subspecies of chimp or another species in the same genus as the common chimpanzee (p. troglodyte), depending on who you ask. Both are descended from the same lineage that split with our last common ancestor, so it is correct to say that bonobos are the closest living (extant) relatives to common chimps, and all members of the genus Pan are equally closely related to h. sapiens.
This in turn leads to some other (intuitively) surprising results, for example that chimpanzees are more closely related to humans than they are to gorillas.
