Tennyo Masaki is the sister of Tenchi Masaki.  Her mother is Kiyone Masaki.  Her father may be Nobuyuki Misaki, but he may actually be Tennyo's step-father.    Tennyo is an almost exact twin of her mother.  She and her mother used to switch places when Tenchi was young.    Tennyo is much older than she looks.  She is currently in her 80s.  It is not explained if Nobuyuki is a normal earthling or is Jurian in the OVA series; this is why he may not be Tennyo's father.

Continuing right where the last OVA series left off, the mysterious Lady Tokimi dispatches the warrior Z to Earth in order to learn more about Tenchi and his connection to Washu and Tsunami. Z is ordered not to lay a hand on Tenchi, but he may have his own agenda as he quickly sets about making trouble for our hero. Meanwhile, Tenchi's father and grandfather come to the decision that it may be time for Tenchi to learn even more about his past and his Jurian heritage. And the arrival of a couple of new female residents to the Masaki household threatens to upset the balance and inflame the rivalry over Tenchi's already decidedly divided affection. 
(Source: Anime News Network)

An official Twitter account and website opened on Friday to announce a Tenchi Muyo! Ryo Ohki Dai-4-Ki (4th Season) project. 
 
(Source: Anime News Network)

After a 'modified' ending to the Choubimaru incident, the punishments for the offending parties is metted-out, as well as a surprise marriage proposal by Misao to Mashisu. It almost didn't happen... until Mihoshi and Misao's mother Mitoto steps in and gives her and her family's approval, much to the dismay of FORMER G.P. Marshall Minami Kuramitsu. Otherwise, life goes on as usual for the Masaki clan. But soon when the question of how Tenchi's mother had died is presented, the answer nearly causes a rift between Tenchi, his father and his grandfather, for which only Tenchi's future mother-in-law Rea can solve... as well as the resolution of Noike's unusual secret. 
(Source: Anime News Network)