I made up this theory today while writing in another post with KBL who helped by contridicting me so i covered more of my holes but im putting it all together here for you to fla.. i mean discuss
What i think happened is that when Ven asked his friends to erase him they erased his body but decided to keep his heart and hide it where they put terra's keyblade to keep Ven's heart safe inside of Riku. Riku had the strongest heart and was the stronger kid of the island making him a better choice than Sora. But after a few years Riku fell into darkness and Sora took the keyblade from him, but while he was taking the keyblade he also took Ven's heart unknowingly keeping the heart safe as it followed the keyblade.
Then we go ahead to when Sora used the dark keyblade on himself and became a heartless but because his heartless form of a shadow couldnt use the keyblade but his nobody could it stayed with the nobody. With Ven's heart inside of him but still out of reach because it wasnt Roxas'/Sora's heart (just like how the Org couldnt just take one of the random hearts from a destroyed heartless they needed either a new heart created from kingdom hearts or their old hearts from their destroyed heartless) it effected him by his apperance and emotions both being in Roxas but not Ven's memories because it was still not his heart. So Roxas had a heart and emotions but as still a nobody and he has the apperance of Ven.
What i think happened is that when Ven asked his friends to erase him they erased his body but decided to keep his heart and hide it where they put terra's keyblade to keep Ven's heart safe inside of Riku. Riku had the strongest heart and was the stronger kid of the island making him a better choice than Sora. But after a few years Riku fell into darkness and Sora took the keyblade from him, but while he was taking the keyblade he also took Ven's heart unknowingly keeping the heart safe as it followed the keyblade.
Then we go ahead to when Sora used the dark keyblade on himself and became a heartless but because his heartless form of a shadow couldnt use the keyblade but his nobody could it stayed with the nobody. With Ven's heart inside of him but still out of reach because it wasnt Roxas'/Sora's heart (just like how the Org couldnt just take one of the random hearts from a destroyed heartless they needed either a new heart created from kingdom hearts or their old hearts from their destroyed heartless) it effected him by his apperance and emotions both being in Roxas but not Ven's memories because it was still not his heart. So Roxas had a heart and emotions but as still a nobody and he has the apperance of Ven.