yanno, after seeing Sai finish off the picture, I can't help but think that Oro took the body of Sai's brother to use as his own. Oro had a body with blonde hair once and we saw him take it over in one of the episodes using his jutsu.

I have a strange feeling Oro's gonna let out that secret and Sai's gonna snap or something.
That's actually a good theory. Since the body Oro took had grey hair and judging from from the picture it seem as if Sai's brother had grey hair as well. Would be an interesting twist if it turned out to be true that Orchimaro somehow procured sai's brother in his dungeon of evil. Sai goes berzerk and desperately tries to fight oro