How to retrieve nested family instances in Revit API -

i'm using filteredelementcollector retrieve family instances:

    var collector = new filteredelementcollector(doc, doc.activeview.id);     var familyinstances = collector.ofclass(typeof(familyinstance)); 

this works fine families don't have nested family instances. if have in project instances of family a, , family includes instances of family b, code doesn't instances of family b. how family b instances?

i'm new revit api , seems there must simple solution couldn't find 1 online. i'm using revit 2015 if makes difference.

the familyinstances have list of families in active view (including nested , non-nested ones).

what need iterate through each familyinstance , see if root family (ie contains nested families) or nested family or none. like:

            var collector = new filteredelementcollector(doc, doc.activeview.id);             var familyinstances = collector.ofclass(typeof(familyinstance));             foreach (var anelem in familyinstances)             {                 if (anelem familyinstance)                 {                     familyinstance afamilyinst = anelem familyinstance;                     // need skip nested family instances                      // since them per below                     if (afamilyinst.supercomponent == null)                     {                         // family root family                         // ie might have nested families                          // not nested 1                         var subelements = afamilyinst.getsubcomponentids();                         if (subelements.count == 0)                         {                             // no nested families                             system.diagnostics.debug.writeline(afamilyinst.name + " has no nested families");                         }                         else                         {                             // has nested families                             foreach (var asubelemid in subelements)                             {                                 var asubelem = doc.getelement(asubelemid);                                 if (asubelem familyinstance)                                 {                                     system.diagnostics.debug.writeline(asubelem.name + " nested family of " + afamilyinst.name);                                 }                             }                         }                     }                 }             }