Sayyed Mohammad Al-Musawi, Sayyed Mohammad al-Musawi is originally from Iraq and heads up the World Ahlul Bayt Islamic League in London. Other than being involved in various humanitarian projects, he frequently responds to... Answered 3 years ago

There ae different opinions among the scholars in this matter.

Al Haafidh Abu Na'eem sated in Hilyat Al-Awliyaa that Ima Al-Ridha had six sons and Jafar is one of them.

Mohammad Ibn Talha al-Shafi'ee had the same opinion. 

Many of our scholars including Shaikh Al-Mufeed and Al-Erbily narrated from Imam Radha (AS) that he wl have only one son (Imam Al-Jawad) and Allah (SWT) will grant this one son lot of sons.