When Fea Kreuz died, I'm assuming that he changed his name (to Kreuz) to reduce the chances of contact between them and people in their previous lives. But as Castor said in Kapitel 33: "Once someone dies, it is prohibited by Heaven for that person to come in with people who knew that death."
But Kreuz and Krom knew each other? If you look, in Kapitel 43, Kreuz calls Krom 'older brother'. So why has Vertrag broken this law? Could it be that Krom was not aware of his brother's death?