Birth by Sleep Connections

Apperently, Sora is connected to Ven, Roxas, Namine, Xion, and possibly more. Well what about Riku and Kairi? We've heard Kairi theories about her being connected to Aqua, Xion, and Namine, and Roxas but what have we heard about Riku's connections? Why does Sora have to be connected to everybody? So much of riku's life we have missed while we watched sora's life but it seems like riku plays a huge part in the series and we are not giving him nearly as much credit as he deserves.

 

Yep it's assumed true right now.

Riku maybe connected with Terra since they make have had similar experience with light and darkness

Doubt it

He's the key that connects it all
And I mean he is the main character of the series everything has to relate to him some way.

There maybe a game to explain what he's gone throught later on, And a game that focuses on the King's story in KH1 as well.

 

He could be, and according to popular theories he is. But as of right now we can only guess at who Xehanhort really is.

 

Yen Sid said that Sora was the key connecting to Destiny Islands, Kairi, Riku, etc. As for the Kairi 'theories' Namine is Kairi's nobody. I believe that Xion was created from data from Roxas and Namine. Namine being Kairi's nobody, that means Kairi was connected to Xion. And It was Sora connected to Terra, Roxas to Ven, and Riku to Aqua. Kairi didn't have much to do with them.

Riku does have a big part in the series. Just look at all the games. He was the one who helped close the Door To Darkness, and he helped Mickey for most of their journey together post Chain Of Memories. In 358/2 Days, he helps Diz, until Roxas disappears and Sora awakes. He also ended up helping Sora and the gang in KH2, i.e. with the ice cream and the photo. And then he was also there for The Castle That Never Was.