Muslims do NOT have cast system. Indian Hindus often use the excuse by using this word ashrafi or ashraf or afzal to argue that there is cast system among Muslims
well there is no such thing ashraf or afzal among Muslims. Ironically this old rant is used in India NOT in Pakistan. Even if we talk about Indian standard then old nawab shawab families have this ashrafi thingy that too was not based on casts but based on social status or wealth. Even today almost every development country has this status divide but this should not be confused with Hindu cast system since despite class divide among Muslims based on their economic conditions there is no untouchability in our religion. in Feudal system yes there is but not in faith.
As far as Syeds are concerned Indeed many families were and even today some are reluctant to marry off their daughters to a non-Syed BUT That is not at all based on any untouchability concept BUT it was due to the fact that syeds being descendants of Prophet Muhammad (PBUH), hence women from that bloodline carry a lot of respect for Muslims and there is fear that one (husband) might not be able to give as much respect to bloodline of the Prophet which the Bibi deserves.
But this trend has changed a lot and now it is common to marry a Syed outside own clan.