Jewish communities had been established for several centuries in the Arabic peninsula before the arrival of Islam. They were especially installed in Yemen. According to historians, these communities were either of the Hebrews having flees Roman repression in IIème century after JC, or of the Arabs converted with the Judaism.
These communities occupied the area of the oases in the North of Yemen and the South of Syria. They were protected by Arabs tribes (system named "hilf") but it's possible that this situation was reversed several centuries before.
The Jewish establishments were significant in Yemen. It's possible that Jews converted with Islam made pass from the judaïc concepts (accounts of the prophets for example) in the Islamic tradition. The Jewish communities were powerful and very structured, very conscious of their identity. In spite of this specificity, the social structures of the Jewish tribes were the same ones as those of the Arabs.