There is a big community of Sayyids settled in and around the Nanganallur region in Chennai that trace their ancestry directly to the Sayyids of Iraq.Traditional Sayyid families rarely marry outside their community, and emphasise marrying into Najeeb Altarfain (of Sayyid descent from both the mothers and fathers side) families. This insistence on endogamy has begun to decline among the more urbanized families, with an increase in exogamy with other groups such as the Shaikh and Mughals.Historically, the Sayyids of Uttar Pradesh were substantial landowners, often absentees, and this was especially the case with the Awadh taluqdars. In the urban townships, Sayyid families served as priests, teachers, and administrators with the British colonial authorities given the community a preference in recruitment. Though they account for less than 3% of Muslim population, they control a majority of economic resources. The community also has a very high literacy rate. The independence and partition of India in 1947 was traumatic for the community, with many families becoming divided and some moving to Pakistan. This was followed by the abolition of the zamindari system, where land was redistributed to those who till the land. Many Sayyids who remained on the land are now medium and small scale farmers, while in urban areas, there has been a shift towards modern occupations.The Sayyids of Punjab belong to the Hasani (descendants of Hasan), Husaini (descendants of Husayn), Zaidi (descendants of Zayd ibn Ali, grandson of Husayn), Rizvi, (descendants of Ali al-Ridha), and Naqvi and their sub-caste Bukhari (descendants of Ali al-Hadi).
They usually exercise their influence through commerce and politics. Tamil Nadu
There are a notable number of Sayyids in Tamil Nadu that mostly concentrate in the cities like Erwadi, Nagore, Madurai, and Kayalpattinam. Badusha Sulthan Syed Ibrahim Shaheed of Ervadi, a Hussaini descendant of Mohammed and a ruler of Madinah, travelled to South India in the middle of the 12th century. His descendants who live in Ervadi with the clan name Levvai are from a single forefather and are Sayyids. The heirs of Shahul Hamid Abdul Qadir badusha of Nagore who live there and are called with clan name of Sahib or Saab or Saabu are Sayyids. Kazi Syed Tajuddin the son of Mufti Jamaluddin al Maabari who founded the Kazimar Big Mosque in the 13th century the first mosque in Madurai is a Hussaini descendant of Mohammed and hence belong to Syed family. Until recently, his descendants (Syeds-Qazis-Huqdars) lived in the same Kazimar Street locality in the center of Madurai city for over seven centuries and managed the Kazimar Big Mosque constructed by their forefather. Syed Tajuddins younger son Kazi Alauddin lived in Kayalpattinam and his shrine is found there.