Saudi Arabia has detained two senior members of the royal family - Prince Ahmed bin Abdulaziz, the younger brother of King Salman, and Mohammed bin Nayef, the king's nephew - according to reports citing sources with knowledge of the matter.The Wall Street Journal reported the detentions of the two royals on Friday and said they related to an alleged coup attempt. Bloomberg also reported the detentions, quoting a source as saying that the pair were accused of "treason".