Baatar Jr. and Kuvira both grew up in Zaofu. Baatar was the son of the matriarch Suyin Beifong while Kuvira was abandoned as a child as raised by Su as one of her own. Baatar Jr. worked with his father as an architect while Kuvira was the captain of the guard. However, one the Earth Kingdom fell into anarchy and Su decided not to get involved, Kuvira decided to leave Zaofu to go help the Earth Kingdom and Baatar Jr. left along with her.
Over the next three years, Baatar Jr. and Kuvira worked together to form the Earth Empire by getting various Earth Kingdom states to join them. At some point, the two fell in love and eventually got engaged. When the two arrived in Yi, they announced their engagement to Opal. Baatar joining Kuvira caused conflict between him and the rest of his family but he cared more for Kuvira. When Baatar's father and brother refused to bow to Kuvira, he was upset and had them imprisoned.
Eventually, Kuvira decided to try and conquer the United Republic of Nations and Baatar Jr. supported her as always. The two embraced while having a heart-to-heart conversation while embracing and Baatar told Kuvira that he loved her. They decided that they would get married after taking over the United Republic of Nations. Korra eventually captured Baatar and threatened to never allow him to see Kuvira again if he did not cooperate. However, Kuvira willing fired at Baatar in an attempt to take down everybody else, but not before lamenting that she did love him. Baatar Jr. felt very hurt and betrayed by this and eventually told Team Avatar how to shut off the colossus.
Baavira is a popular ship in the Legend of Korra fandom. It became popular as soon as Book Four: Balance aired and the two were revealed to be engaged. Many fans did not trust Kuvira and were worried that she would turn on Baatar Jr. or vice versa due to the latter's family. This turned out to be correct as Kuvira willing fired her weapon at Baatar Jr. in an attempt to take down her enemies. Some speculated that she did still love him though and this turned out to be correct.
- According to the commentary for Book Four: Balance, Kuvira did love Bataar Jr. even though she was willing to kill him in order to get to everybody else.