There are many sunni scholars who mention the birth of imam Mahdi and accept that he is the awaited Mahdi according to what the prophet said and there are many others who mention the birth of (the son of imam Hassan Al Askari named Mohammad(PBUT) but don't believe that he is the awaited one.
Both parties agree upon the date of birth and the name of the son of Imam Hassan Al Askari. If you would like the sources please let me know.