Now, if this is explained in Aqua's story, say that and no more and I'll figure it out. I completed Terra's and Ven's story.
 
Anyway, after the first battle with Vanitas as Ven, you (finally) get rid of his helmet. Since he's Ven's dark side, you expect him to look like Ven...
 
...WTF he's Sora with BLACK HAIR! That's the only difference. He's even voiced by Haley Joel Osment. Who voices Sora.
W.
T.
F .
Is there an explanation for this in the Final Episode, Aqua's story, or the secret movie? (I'm playing on Proud so I'm bound to see it).  Please help me with my confusion (but no spoilers. If you have non-spoiler speculation. Fire away.)

Major Spoilers about Ventus.
 

" Major Spoilers about Ventus.
 

SPOILER WARNING: Click here to reveal hidden content.

1. Master Xehanort seperates the dark half of Ven's heart, this dark half forms a body around itself and takes on a will of it's own thus Vanitas is born
2. This act damaged Ven's heart so much that he would soon die, MX took him to Destiny Islands to die
3. While there, Sora had recently been born, Sora's heart connected to Ven's heart to fill the gap left by the loss of the dark part of Ven's heart, A.K.A Vanitas. This healed Ven's heart and allowed him to live.
4. However Ven still lost his memories, and MX took Ven to Eraqus so Ven could become stronger in the hopes he could use Ven and Vanitas to forge the X-Blade one day.
5. Eventualy Ven and Van's hearts merge into 1 heart and the X-Bade is formed. Ven destroys Van's heart and therefore destroys his own dark half of his heart and the X-Blade. This damages Ven's heart so it leaves his body and goes to Sora's heart to sleep and heal.
6. Because Ven lacked his darkness he had a heart of pure light and therefore his body did not fade but went into a comma like Kairi's did
7. 10 years later in KH1 when Sora became a heartless, Ven's heart went to Roxas and thus Roxas looks like Ven. When Roxas returned to Sora, Ven's heart also returned to Sora and that is where his heart is currently. 

"

Still doesn't explain Vantias' looking like Sora. Vanitas was separated BEFORE Sora's light merged with Ven's heart.