Hello JillBean
Welcome to the SBB Community.
A transfer is not possible. You could all use his account provided he has purchased the STP with a user account and not as a guest. The same account can be used on up three devices.
If he has indeed purchased the STP with the guest option, you can only use the PDF copy, to be saved on your own device and show it from there.
All must have their physical passport (no photos, no paper copies) with them when using the Swiss Travel Pass.
Kind regards,
Roland