While many yōkai have acted as allies to Kitarō in the original manga and across the many adaptations, the Kitarō Family is generally considered to refer only to the core group of allies who appear in all or most works.
NOTE: Manga starting points refer to each character's first appearance in the Shonen Magazine version, as that is considered the beginning of the heroic era of the franchise.
Medama-Oyaji - Beginning with the manga story The Birth of Kitarō and the 1968 anime. Medama-Oyaji is knowledgeable in most things yōkai and as such usually provides information on each villain yōkai.
Nezumi-Otoko - Beginning with the manga story Obake Nighter and the 1968 anime. Nezumi-Otoko constantly betrays Kitarō and the Family but is always let back in the group, whether because he has a change of heart, Kitarō forgives him or simply so Shigeru Mizuki can keep the status quo. While he usually only helps Kitarō for personal gain, he has been known to occasionally help out for selfless reasons.
Konaki-Jijii - Beginning with the manga story The Great Yōkai War and the 1968 anime. He is primarily a fighter but has been known to provide information on enemy yōkai much like Medama-Oyaji.
Ittan-Momen- Beginning with the manga story The Great Yōkai War and the 1971 anime. While he made a handful of appearances in the 1968 anime, Ittan-Momen didn't appear regularly until the 1971 series. He primarily acts as transportation for Kitarō but is also a good enough fighter that he has been trusted to lead teams into battle occasionally.
Nurikabe - Beginning with the manga story The Great Yōkai War and the 1971 anime. Like Ittan-Momen, Nurikabe rarely appeared in the 1968 anime, but appeared more frequently in the 1971 series. Nurikabe's main role in the team is to act as a shield.
Yuki-hime - Appeared only in the manga series Yuki-hime-chan and GeGeGe no Kitarō. Was said to be Kitarō's long-lost little sister, but has never been mentioned since. Had telepathic powers which often made her the target of evil yōkai.
Netarō - Appeared only in the manga series Kitarō Kunitori Monogatari. Originally believed to be Kitarō's long-lost brother, he is in actuality the prince of the Mu Empire seeking Kitarō's help in freeing his people.
Yobuko/Yama-Kozō - Beginning with the manga story Kasa-Jizō and the 1968 anime. Frequently appears as a Family member in the manga but makes far fewer appearances in the anime adaptations.
Bake-Garasu - Beginning with the manga story Yasha and the 1968 anime. Yōkai crows who act as messengers to Kitarō.
Tsurube-Bi - Beginning with the manga story Mōryō and the 1968 anime. Frequently appears alone, but in some adaptation acts as the leader of other flame yōkai.