Wikipedia
الموسوي translated as Al-Mosawi or Al-Musawi (, pronounced Mūsavi in Persian), is a surname that presumably indicates a person comes from a prestigious and highly respected Middle Eastern family with a transnational identity. Members of this family are referred to by the Anglicised version of their name as Hashemites. They are usually given the honorific title Sayyid before their first name. The literal translation of the Arabic word Sayyid is Sir or " liege lord" in the English language. This family is mainly based in the Mesopotamian region, they also live in other Middle Eastern, most notably Iraq. Though no written records or genetics studies done on this family, verbal history claims that the name implies that this person is a direct descendant of the Islamic prophet Muhammad through the seventh of the Shi'a twelve Imams: Musa al-Kazim ibn Jafar as Sadiq who is a grandson of Muhammad. Other transliterations include Musawi, Mosavi, Mousawi (Arabic transliteration), Moosavi (Persian transliteration), or Moussaoui (in the French transliteration) Moosawi (Bahraini translation) Al Mosawi (English translation). Also some Mousavis take the last name of Kazmi. Many Al-Mosawis migrated from Mecca and Madina Saudi Arabia to a small village that their ancestor Musa Al-Kadhim built in Baghdad Iraq. Large members of this family are located in Iraq, and they are also located in other countries such as Iran, Lebanon, Kuwait, Bahrain, Qatar, UAE, Saudi Arabia, and other Arab countries, Afganistan, Pakistan, United States Of America, The Netherlands and the United Kingdom.
Al-Mosawi family is an influential Middle Eastern family because they are directly descended from the 7th Shia Imam Musa Al-Kadhim who is the son of Imam Ja'far al-Sadiq son of Imam Muhammad Al-Baqir son of Imam Ali Zayn al-Abidin son of Imam Hussain son of Imam Ali Bin Abi Talib and the son of Fatimah the daughter of the Muhammad. Members of the Al-Mosawi family are called with the title Sayed literally means Mister or Sir. As an honorific title, it denotes males accepted as the direct descendants of the Muhammad.
The roots of the Al-Mosawi family is supposedly claimed to be Arab that comes from the Head tribe of Banu Hashim, a clan of Quraish which makes them Adnani Arabs or Northern Arabs who are originated from Ibrahim through his son Ishmael in Mesopotamia which is nowadays Iraq in the ancient city of Ur near Nasariyah in Southern Iraq. Many Arab tribes trace their lineage through Adnan who is the Father of the Arabs that traces his lineage to Ishmael the son of Ibrahim the great great grandfather of the Adnani Arabs.
Although no statistical data available to the day, but it is believed that most members of this tribe adhere to Shia Islam the Twelvers or Jafari approx 90-95% of the family are Shia muslims the rest are Sunni Islam which holds the name of Hussaini Al-Musawi and other noticeable Mosawi family names.