Po: But you don't even know kung fu.
Li Shan: Then you will teach us.
Po: I can't teach you kung fu! I couldn't even teach Tigress, and she already knows kung fu.
In Kung Fu Panda 2, Shen says he waited 30 years since he destroyed the Panda village, and Po was just a baby at the time. However, in Kung Fu Panda 3 Mr. Ping says he raised Po for 20 years before he told him he was adopted.