Manga Origins: Dosu Kinuta

First Appeared in Naruto Chapter 35 in the Manga. Debuted in Episode 21 in the Anime.

the Sound Ninja who seen through Orchimarus plans who ultimately wanted to kill Sasuke on his own accord.

This is more or less a test, simple ground, I did my best to actually look up his background and childhood but it's best to assume that Dosu like all others who were gained by Orchimaru, was recruited when he was a child.
Music:

Hokage Tower - Naruto Clash of Ninja 2-4

Footage:
Naruto Episode 23-53
Naruto: Ninja council 2

First seen:
https://www.youtube.com/watch?v=PJpE2nnAxrs