There are two ways to check whether a children’s subscription has been automatically linked to the Swisspass of the parents or accompanying adult:
Either, you log into your account at www.swisspass.ch and check the link under “Subscriptions”.
Or you start the SBB app, for example, open “Billette & Swisspass”, then tap on your profile photo, “Show subscriptions” and “To the Swisspass account”. All your valid public transport subscriptions will now also be displayed. And further down you should now find the child subscriptions linked to you. (sat)