Cloud gaming and consol gaming at same time

Hi - i have one Xbox series X with a parent account/ profile and two seperate kid's profiles.

How do i allow one kid to play on the consol itself and another to play on an iphone at the same time. Whenever i connect to the xbox app on the iphone it logs onto the consol.

I want them to be able to play seperate games at the same time - how is this possible?

:)