Are Sogeking and Usopp the same person?

Sogeking is Usopp’s alter-ego that he developed during the Water 7 and Enies Lobby Arcs after he left the crew. Later when he saw the others trying to save Robin, it made him feel guilty for leaving, so he stated to Sanji and Franky that he cannot help them fight for this reason.

Did Luffy know Sogeking is Usopp?

Anime Reference: As you can watch in this scene, it’s not that Luffy finds out that Sogeking is actually Usopp. It’s just that he introduces himself as: Luffy and Chopper: Sogeking from the Sniper Island? Sogeking (Usopp) : That’s right!