Sharif
Sunnis in the Arab world reserve the term "sharif/sherif or shareef" for descendants of Hasan ibn Ali , while "sayyid" is used for descendants of Husayn ibn Ali , Hasan's younger brother . 
<triplet> Hasan ibn Ali <subj> Husayn ibn Ali <obj> sibling <triplet> Husayn ibn Ali <subj> Hasan ibn Ali <obj> sibling