AU explanation here: http://www.furaffinity.net/view/33422626

Here are a couple looks into the childhood of Mao Mao and his adoptive little/younger brother Bao Bao:

On the left, Mao Mao, at times, teases Bao Bao about him being a dog as though dogs were pets or servants (not maliciously, to be clear). Bao Bao does find the joking remarks to be in rather bad taste, understandably so.

On the right, Mao Mao shares with Bao Bao his own aspirations to be a legendary hero just like his dad and sisters. Bao Bao is easily impressed by this, looking up to his big brother and hoping that he would show him how to be a hero too.

(Extra note: Whenever Mao Mao performed a trick and his dad wasn’t looking, Bao Bao was looking at him instead, and would ask him about how he did the trick whenever he had time.)