UIDocument uidoc=this.ActiveUIDocument;
Document doc=uidoc.Document;
Selection sel=uidoc.Selection;
Reference hasPickOne = sel.PickObject(ObjectType.Element);
ElementId el=hasPickOne.ElementId;
Element element=doc.GetElement(el);
FamilyInstance familyinstance=element as FamilyInstance;
Family family=familyinstance.Symbol.Family;