There is a special phenomenon of ascribing family relations between individuals in a society. This social symbolic status may have its own nature (as indicated by this hierarchy position) of we could consider it as a subclass of social status or of function> to be safe I have just put it as a kind of institutional fact. While it may indicate a general function within society or with regards to the individuals in the relation, likely this famillial relation can be considered separate also from function, simply as indicating a symbolic distributino of relations which are then assigned functions.... it's tricky.