This is not possible out of the box and I don't know of any extra that archieves what you want. You would have to write a plugin that acts everytime you save a resource and split up the content, create/delete sibling resources as needed etc. Sounds like a lot of work for what you want to archieve to me.
I suppose you have a look at the MIGX extra. It provides you with a TV with the possibility to store an indefinite amount of distinct TV content sets. Have a look at the documentation and Mark Hamstra's tutorial (with screenshots) to see how it is done. You should define one MIGX entry to consist of a text field for the <h1>
and a rich text field for the content of the "subpage".
Afterwards, you can use form customization to hide the original content field and display your MIGX Tv instead.
I think, this is a much easier way to archieve, what you want, and can't think of any way, where you would benefit from actual subpages.
Edit: Sorry, I just recognized that you were asking about Evolution, not Revolution. My solution would work in Revo, but I don't think there's something like MIGX for Evo. Sorry, my mistake.