open subpage inside page?

hi!

i’m working on a wordpress site and i want to open a subpage inside the page that has the subpage. for example, I have a clients page called “clients”, in the clients page i list the clients, and when i click on one of the clients, i still want to have the clients listed and the headline clients..

i tried with the “is_subpage()” funtion, but i could not get it working, because i want to collect the page, the page subpage that you are visiting and the links to the other subpages.

i managed to do almost the thing with the plugin “Category Page”, but that was with posts, and i’m not gonna build it that way. anyone that knows if there is anything like that for pages?

thanks!