As we all know, Osiris is a black male, thats why he is symbolized on the egyptian flag as the black stripe.
Furthermore Osiris is known for his fancy golden bracelets n'shit.
Origin of Osiris
He saw God who was busy creating the world. God was clearly very busy and Osiris didnt want to interrupt him.
Hence Osiris sat down on the surface of Venus and took a rest.
When God was done and the world was ready to be released on Steam, Osiris gave God a bottle of Champain as a gift for the opening ceremony.
After winning Gods attention he was allowed to create the egyptian empire.
Creation of Egypt
Osiris wandered trough the lands and seas of the earth until he stumbled over a pretty river called the nile.
"let there be an ancient civilization near this pretty river.", Osiris said.
When the year 1993 finally began the egyptians started to cultivate the land.
Osiris watched over the land and over the simple lives of the citizens.
This went on for many years during 1993 until the egypts discovered how to forge iron and how to tend cows.
After a while, when the egyptian empire grew and grew, Osiris had more difficulties managing the whole thing.
There where many administrative obligations Osiris was not aware of at the beginning.
Therefor he summoned Tutankhamun as his representative an later the Pharao of Egypt.
Relation to Tutankhamun
In the beginning, Tutankhamun was the student of Osiris.
He had to learn how to rule over an ancient empire.
Then Tutankhamun became the Assistant of Osiris.
He adopted more and more responsibility for the nation.
And at the end he became the Pharao of Egypt, ruling over the whole nation, with Osiris as his supporter.