The tiger cub is a cub Fu befriends in book 1
Tiger book 1
The tiger cub is captured and his mom is eventually slain in a tiger trap. The soldiers captured him in a net. Fu rushes in and scares the soldiers and mayor, while knocking one out and the mayor's son. He nurses the cub. The cub is nursed to health and rests with Fu for that night. Fu learns that the mother killed the mayor's wife,developing a taste for human. The cub was going to be killed, since being taught to kill people. Fu was later captured by Ying. Malao and Fu got dispatched by Ying. However, Ying's second in command, Tonglong, freed them. Malao's snow monkeys scared the soldiers off, the tiger came into the battle, scaring them. Fu and the cub said one more good bye, before the cub ran into the forest.
Not much is known about the cub's temperament. It is shown it is brave and independent like Fu. It is also strong since it overpowered a soldier with quaing, despite his young age.