This is just a thought. I've always thought that Luca didn't expect to be invited just because of his relationship with Don Vito and the family. I think Luca may have had a self-depreciating opinion of himself--at least with regard to Don Vito. He seemed very nervous before seeing the Don--repeating and repeating his lines as if he were to speak to the Pope or something. He was amazed that Don Vito thought enough of him to invite him to the wedding. I don't think that Vito feared Luca, I always felt that Don Vito was only annoyed at having to talk to Luca on his daughter's wedding day. After knowing the reason that Luca wanted to see him, he probably felt like a heel and then decided to allow Luca to see him. I just think that Vito felt a little annoyed that Luca wanted to see him until he found out why Luca wanted to see him. I'm probably wrong about all of this because all of this is just my impression of the scene.

~ Sadie