Branch of Islam that supported Ali Muhammad's son-in-law?

Answer 1

Shia Muslims believe that just as a prophet is appointed by God alone, only God has the prerogative to appoint the successor to his prophet. They believe God chose Ali to be Muhammad's successor, infallible, the first caliph (khalifa, head of state) of Islam. Muhammad, before his death, designated Ali as his successor.Ali was Muhammad's first cousin and closest living male relative as well as his son-in-law, having married Muhammad's daughter Fatimah.

Answer 2

The branch of Islam that believes that Ali, Muhammad's (S) son-in-law, should have been the successor to Muhammad is Shi'a Islam, commonly referred to as Shi'ism.

They believe that, just as Allah chooses the prophets, he chooses the successors to the prophets as well. They say that Allah chose Ali to be Muhammad's successor and that Muhammad announced this before his death. After the death of the Prophet (S), Omar, Abu Bakr, and Abu Ubayda met with Medina's leaders and appointed Abu Bakr as the successor, or Caliph, to the Prophet. Ali and his family didn't like this, but accepted it so that unity could be kept in the early Muslim community. Ali eventually became the fourth, and last, Caliph to the Prophet (S).