ok here is how i feel about three topics: Kairi to the island, Ven looks like Roxas, and this may be the most stupid, but Sora and Riku's parents.
we have all seen the BBS movie rite? well rite before Ven got Blizard cast on him by the U.E.M, he had this weird dark aura-like-thing on his arm, and u no how in each game (ex-cluding CoM) there are new spells and some get the cut? well that might be the game were poisen is a spell. hence the conversation were Ven is on the Town Destiny Island ( not the first real level in the first game, the one the kids play on) he is talking to a guy with a shadow that resembles Riku. i think that Sora and Riku's dad's new about the heartless and that stuff very secretly, and is discussing putting his heart in a future keyblade master. he will choose Sora. BUT does that explain Sora and Kairi's hearts being the exact same? No! what i think is that Ven is Kairi's father ( i have no idea who the mother is, possibly Aqua, idk) and he knew that she was a princess and took her heart because he knew she was going to be hunted one day and fused her heart with his, and thought about putting it in a keyblade master. but he didn't know, and i am probably WAY off, but her grandmom (as seen in KH1 when Sora is becoming a heartless) has her heart taken and becomes Malleficent and tries stealing her heart but realizes that she is no longer in possession of it she gives her amnesia other than her name and randomly sends her to a different world. (also as a side note during that scene they are in the HB library so they either were royalty there, related to the real Ansem, or something else randomly). also the parents didn't look for SRK but they could have sent a reply by bottle like Mickey at the end of 2.
If u have any objections, suggestions, coments, or missing things, please comment here.