something fishy in kh fm+

No they died. We never see them. Their portals in kh2 are destroyed and gone. If you mean the journal. It's just added in case people didn't play khcom and stuff. Plus to show all 13 members.

 

And the secret cutscene about zexion talked with xigbar, it's happened when they had marluxia as their new member

 

First yes, and don't double post spam stuff. It is a flash back just like the many Roxas has in regular KH2.

 

Cause once Ansem left, Xehanort took it over, and Xehanort became a heartless and Xemnas got it and took over it.

 

Well, the reason that the 4 organization back there in Castle Oblivion are 'alive', is that they are only datas.

It's just like a little add-on to the game. That's why the characters, don't talk on the first cutscene to start a Data fight, for example Marluxia.

It shoudn't change the main storyline, and better yet, it hasn't.

 

You've got it all wrong. Yes they did die in CoM, but in FM there called.

An Absent Silhouette is a "ghost" version of a member of Organization XIII who had already been slain. It appears as an extra set of challenges in Kingdom Hearts II: Final Mix+. Whenever Sora challenges an Absent Silhouette to a battle, the Absent Silhouette takes the form of the slain member it represents and fights him. There are five Absent Silhouettes in total: Vexen, Larxene, Lexaeus, Marluxia, and Zexion. All of them died in Kingdom Hearts: Chain of Memories.

At first, the Absent Silhouette looks like a sphere of darkness with nothingness and the slain member's element circling around it; a picture of the slain member's weapon is also featured in the center of the sphere. When Sora accepts its challenge, it warps Sora to wherever its member was last fought, with the exception of Marluxia's, which is the area of the second to last battle against him. There, it challenges him to an extremely difficult battle.

An Absent Silhouette usually bears a different fighting style than the member originally exhibited in Chain of Memories. For example, Larxene often threw her knives and Zexion created copies of himself using the stolen skills of his opponent. However, in Final Mix+, Larxene's Silhouette favors using copies of herself for speedy attacks from all directions, and Zexion's favors trapping his prey into a dimension within his weapon, a lexicon.