Is "Most notable was the appointment of Marwan ibn al-Hakam, Uthman's first cousin, as his top advisor, which created a stir among the Hashimite companions of Muhammad, as Marwan along with his father Al-Hakam ibn Abi al-'As had been permanently exiled from Medina by Muhammad during his lifetime." a good answer to the question "Who was the son of Al-Hakam ibn Abi al-'As?"
yes