Didi 弟弟

We haven't yet trained Kanyon how to say "Corbin" so he simply refers to his brother as "baby" or "didi".

Didi 弟弟 means younger brother.

Corbin would call Kanyon "gege" meaning older brother. This is what is so cool (and sometimes difficult) about Chinese. The noun often denotes the rank, relationship, or age of the person you are referring to. Here are some other examples from the family:

Gege 哥哥 means elder brother
Jiejie 姐姐 means elder sister
Meimei 妹妹 means younger sister

And there are plenty where these come from. There are words for paternal Grandfather, paternal Grandmother, maternal Grandfather, Maternal Grandmother, an uncle whose my dad's gege, an uncle whose my dad's didi, an aunt whose my dad's jiejie, an aunt whose my dad's meimei, etc. And that's just on the paternal side. There are more for the mother's side of the family and we still haven't gotten to relatives that far removed. Yikes!