multiple window application

 I have code that creates 2 windows using one event loop. It's not deep 
into the weeds yet, but upon the creation it produces 2 'dock' icons, 
capable of un-maximize. I can also position the 2 during 'reparent' and 
retain positions (configure) for un-max. My question: is the grouping 
of windows under one icon a window manager response, or do I need to 
create 3 windows, the first being a not mapped root window (size of 
display) with the 2 windows as children of the 'fake' root? If this is 
a window manager response, the single icon for 2 windows, what might 
the keywords be to produce some kind of clue to duplicate or use of 
this feature? The intent is to look like one application to a user.
 Steve