Where Is Al-Mahdi Now?
Question

Will the expected Mahdi resemble the Messenger (peace and blessings of Allah be upon him)? What about the voices that have emerged in recent times and claim that he is here and has been born, i.e., he exists at present?
Praise be to Allah.Who is al-Mahdi?
The appearance of the Mahdi at the end of time, when he will fill the earth with justice and fairness after it had been filled with injustice and wrongdoing, is something that is mentioned in the authentic Sunnah, and some of the scholars of hadith said: The hadiths about the Mahdi are mutawatir because of their large number, and the descent of ‘Isa ibn Maryam (peace and blessings be upon him and our Prophet) and his praying behind him is something that is well known. 
What is the name of Al-Mahdi?
The name of the Mahdi and the name of his father will be like the name of the Prophet (peace and blessings of Allah be upon him) and the name of his father; he will be one of the descendents of  Fatimah (may Allah be pleased with her).  
The Mahdi who is mentioned in the hadiths is not the so-called awaited Mahdi mentioned by that deviant group, the Ithna ‘Ashari (Shi’ah) who claim that he entered the tunnel and is awaiting the order to emerge, and whose name they say is Muhammad ibn al-Hasan al-‘Askari. This is an illusion and a myth, and the refutation of that is discussed in books, and there is no room to go into it here.  
But we advise you to read Minhaj al-Sunnah by Shaykh al-Islam Ibn Taymiyah and summaries of it such as Manhaj al-I’tidal by al-Dhahabi, and Tuhfat al-Ithna ‘Ashariyyah by Muhibb al-Din al-Khatib. 
It is essential to note that every group is awaiting a Mahdi such as the Jews who are awaiting the Mahdi, but for them he will be the Dajjal who will be followed by the Jews of Isfahan. 
The Christians are awaiting a Mahdi which is the descent of the Messiah (Second Coming of Christ). 
We Muslims have no doubt about the descent of ‘Isa ibn Maryam (peace be upon him), when he will break the cross and kill the pigs, and will abolish jizyah and rule according to the Shari’ah of Islam, and at that time there will be no war. 
Throughout history, there have appeared liars who claimed to be the Mahdi. Some historians have counted them and said that there were more than thirty of them, including Ibn Tumart in Morocco and the Mahdi of the Sudan, etc. 
Where is al-Mahdi now?
As for the view that Al-Mahdi exists at present and that he has been born, this is merely a claim that is made by some people, but there is no evidence for it. It is most likely that it is a myth. 
The hadiths that have been narrated about the Mahdi do not mention where he will be born or when, and they do not tell us to look for him or to bring him up, rather they say that Allah will prepare him in a single night and that the Muslims will swear allegiance to him as their caliph and will be united behind him. 
When will that happen? Only Allah knows. 
 And Allah knows best.