I want to know the answer to the following question:
Who is the elder brother of Musa al-Kadhim?
All the background I'm provided with is that "The Ismailis believe that whether Imam Ismail did or did not die before Imam Ja'far, he had passed on the mantle of the imamate to his son Muḥammad ibn Ismail as the next imam.". Is that enough to answer the question?