share ultimate gamepass subscription

Hi,

Im sure someone must have asked this before, but I cant find it: How can I share my ultimate gamepass subscription with my kids?

My kids are linked in my family account and we currently share gamepass games.

I can play xbox games on my cellphone, so my subscription is working. My kid can play my games through the gamepass app on his xbox. So that all works.

Its just that on his tablet, when he logs on via gamepass, he isnt able to play cloud games. He is invited to subscribe to gamepass ultimate, but even if I want to pay an extra subscription fee, there is no option to upgrade his account to gamepass ultimate.

Thx.

:)