I meant the main window. Do you call show() somewhere in main() before starting the event loop or are you calling show() after creating the children?
No. I will not be calling the show() I will call the show() on Main Widget After creating the child widgets and it is after the event loop starts.

By default all widgets are not yet visible and need to be shown. Children are shown with their parent unless they have been explicitly hidden.

So it depends if your main window has already been shown at the time of child creation. If it has, then the children will remain hidden (their parent didn't get shown after their creation).
It has answered my query and concludes that each child widgets needs to be shown when they are added after the event loop starts.
Is this an MDI application? Are you using QMdiArea?
No, it's not designed using QMdiArea. We are considering each QWidget as a Window and it is serving our purpose.

Thanks for the support.


Regards
SRaju