There's no "Chiyo Family" yet as of Heavenfall, just a loose affiliation of Kara and Tsubo's friends and proteges. After a 10-15 year time jump, though, the family will actually formally exist; Chiyo will be about 19-24 years old and will have taken up the administrative side while her parents step back. So there could actually be "Chiyo Family" player characters. Here's what we've got:
The Chiyo Family: +1 Reflexes
Founded by a bushi and shugenja couple who became friends and confidants of Shiba, the members of the Chiyo family are united in purpose and philosophy despite their different styles of training. While the Jiyo protect the Emperor’s body and the Yuzuru counsel peace and unity in his courts, a Chiyo samurai’s duty is to nurture the Imperial Families’ connection with all of Rokugan, from the land itself on up. Chiyo priests are often found tending shrines in the new Imperial Capital, but many members of the family also travel extensively, visiting remote shrines and villages and collecting information about regional conditions, natural disasters and fortuitous occurrences, and the mood of local nature spirits. If a province is suffering from bandits or famine, expect a Chiyo scout to arrive to gather the news--or a Chiyo shugenja to enlist the help of the local kami. Although it may be many years until Shiba’s Empire has a formal place for “magistrates,” some Chiyo samurai are also called upon to investigate and arbitrate problems in the course of their travels.
Recent historical details (probably still relevant to PCs in Dawn 3, less so a few more decades on): Besides his consort-to-be Yuzuru, two other Ayakashi tribesfolk followed Shiba in the wake of the Tournament of the Kami: Tsubo, a kind and practical woodsman, and Karanoko, a spiritually enlightened mystic and weaver. During the early years of Shiba’s reign, Karanoko and Tsubo supplied support and counsel to the growing Imperial household, encouraging Shiba to ground himself in the physical and spiritual landscape of the Protected Lands that would be Rokugan. The informal group of shugenja, scouts, and emissaries that formed around the pair was eventually organized as a Family under the leadership of their eldest daughter Chiyo, born in the same year the Kami fell to earth. Chiyo became a precocious shugenja under her mother’s tutelage, while her younger sister Niko, who was only a little older than the Emperor’s eldest child, learned the ways of the land and self-defense from their father.