John is Allen Walker's biolgoical father,his last name is uknown
Though Allen thinks his biological parents abandoned him,he is actualy wrong in fact it was for his own saftey. Allen's mother Christine died giving birth to Allen. John,who was a religous scientist knew his son's arm was innocence and knew that this ment his son due to recivng innocence at birth would mean he would play a major role in the battle between The Black Order and The Mellenium Earl.Because of this The Earl attemped to kill both John and his son,soon John erased his son's memory of him and hid him before getting stabbed with the sword of exorcism which John found out The Earl stole it. He said his last words to the Earl
"You think you won Adam.....your wrong my son is safe from you......like I said I would die for my son......and he will put and end to you.....and before you say I am using my son as a tool once again you are wrong.......your days of terror will be over soon......and also tell Neah my son is not his new body......and to my son,remember your father loves you very much......"
John's ancestors where known to have inherited Innocence in a random generation, explaining Allen's inheritance of Innocence, John was also a good friend of Mana Walker.