Wow....

? No, he raped him to turn him into a Vampire too.

The one who turned Sein is not his brother it copied his brother form.

No. It was his brother. Didn't you get the storyline? oô

I do think so too. It's not his brother. The last chapter did show that verloren has taken up sein's brother's form.

(づ￣ ³￣)づ

Verloren was not Sein's brother. That is why he was able to find his brother's head in the sea of bodies in Verloren's soulscape. Verloren had killed Sein's brother when they were fighting in the Crusades. Had Verloren actually been Sein's brother, his body would not have been among the sea of corpses, since they were the bodies of Verloren's victims - every person he ever killed by feeding. Verloren just used the brother's face to manipulate Sein because he knew how much Sein loved his brother.

The reason why Verloren turned Sein instead of killing him, I think, was to eventually have Sein kill him and free him. I can't imagine the idea of living for eternity in a hell of your own making can be much fun after the first few thousand years. He needed to have an escape plan and chose Sein. Having a companion in the meantime may have also played a role as well. As for, "why Sein?" His brother rode out to the front line alone. Verloren likely encountered Sein's brother before he got to the front line. Then, Verloren "played with his food" and perhaps talked with Sein's brother, who would have proudly spoke of the brother he left behind protecting the village. Verloren then attacks and kills the brother. Taking his form, Verloren appears at the front line and decimates the opposing army. He returns as the brother, a conquering hero. Now he is within arm's reach of having both a companion and an escape from torment in Sein. You kind of have to read between the lines through both volumes to grasp the underlying, untold story.

It wasn't specific enough. It could have gone either way. It could have been that the one who killed and change Sein was his brother that was changed into a vampire. But since Sein said that "vampires are able to transform into the likeness of any whom they have robbed of life through feeding" it could be that the vampire will kill his brother through feeding took on his form and came back and place of his brother. But Sein also said that "it comes at a cost one loses ones own original visage forever" at the time his brother was fighting a war so after he became vampire if he killed through feeding it cost him something so at the same time it could have been his brother but he lost something of himself because of the feeding. Sein asks where is he (his brother) when he's trying to kill him but that doesn't necessarily mean that it's not his brother it's just not him that he was before he became a vampire.
Personally I think that it was his brother originally but once he became the way he is now he didn't consider him in the real him anymore. Sein says he'll never become like him meaning he believes that he could become that way too then it won't be the real him.

There all settled(▰˘◡˘▰)

Well whoever it is. The manga is a good read

One simple fact dissolves your theory. How can Sein's brother be the vampire that turned Sein when Sein found his brother's body among Verloren's victims in his soulscape? If Sein's brother is a vampire, he's not dead and would not be among the victims in Verloren's soulscape. Verloren killed Sein's brother and took his appearance. The cost of losing their appearance is paid by the vampire, Verloren. He spent centuries in the appearance of Sein's brother and now can't remember what he used to look like before he changed, this is also mentioned in the soulscape scene. Sein already knows that Verloren is not his brother or he would not go searching for his brother in Verloren's soulscape. Sein knows his brother is dead and he knows Verloren killed him. That is the whole point of the soulscape scene. The reader learns that Sein loved his brother, Sein's brother went off to war alone, he then met with Verloren and was killed, Verloren then returns looking like Sein's brother and turns Sein. The mangaka practically holds your hand as she walks you through those scenes. Sein did not find himself among the victims in Verloren's soulscape, yet he was turned by Verloren. He did find his brother though. That means that Verloren killed Sein's brother, he didn't turn him.

I already explained that it's the him before he killed all those people. It changes you when you feed until you kill. That place doesn't have actual bodies it's like Spirits or dead Souls. Those Are the souls that he killed, he killed his own soul or spirit when he fed on all those people until he killed them. I don't know why you're arguing. It's not like I was choosing sides I was explaining how it could be either way. （￣へ￣）

Other words it's the part of him he lost.