password protecting 'child' pages behind a 'parent'??

I have managed to set a password to protect a ‘members only’ page.

There are several ‘child’ pages behind this header ‘parent’ page.

However it would appear that it is possible to go straight to the ‘child’ pages without having to enter the password on the ‘parent’ page.

I had thought that by putting the pages as ‘children’ to a password protected page, that this would automatically extend the password protection to the ‘children’.

Ideally i only want users to have to put in one password to access their members only area, rather than enter a password to access each page.

Any advice?
Thank you