Returns the first sibling of the given member.
This function returns a member
This function examines all the children of the parent of the given member, and returns the first member of that set (considering the default order of that set).
This function can return the same member that you specify as an argument (if that member is the first sibling).
SELECT MEASURES.[%COUNT] ON 0, birthd.[Mar 2003].FIRSTSIBLING ON 1 FROM patients