Rasulullah said:
Narrated Abu Huraira: Al-Hasan bin `Ali took a date from the dates given in charity and put it in his mouth. The Prophet said, "Expel it from your mouth. Don't you know that we do not eat a thing which is given in charity?" (Bukhari and Muslim)
This hadith clearly outlines the impermissibility of a "syed" person (someone proven to be from the lineage of rasulullah) receiving sadaqah from anyone else.
Is it permissible for them, then, to receive zakah?
Some groups and individuals believe other things about someone who is syed. That's fine, but don't answer this question with things like "syeds can take zakah" or "syeds can take zakah from syeds," or other beliefs. This is a clearly-stated axiom of my question.
Also, this question ignores the largely modern issue of actually proving someone is syed. Don't go there; that's a tangent, and something a lot of people claim to today. Again, the assumption is that you can or have verified that someone really IS syed.