The first person who due to ignorance of Imam Mahdi (hgr)’s birth, denied the birth of Imam Mahdi (hgr), was Ja’afar (the Imam’s uncle)!
Ja’afar used to strongly inhibit the news of the Imam’s birth!!
Ibn-e-Hazm in the book “Al-Fasl fil-Milal…” impeached [Imam Mahdi’s (hgr)]’s birth. He wrote that Imam Mahdi’s (hgr)’s birth didn’t occur till Imam Askari (pbuh)’s martyrdom!

Muhammad Asa’af Al-Nashashibi says, “Imam Askari hadn’t had any son or daughter during his life.
But as for lots of Shi’a and Sunni sources about his birth, these locutions was not only historically wrong, but also they seem more of prejudice and manipulation disease.

“Milad”, the articles collection about birth of Imam Mahdi (hgr), P.45