Hello @eguidotti
Thank you for your question.
No, it is not possible. One of the GA in the same household needs to be one of the following the basic AG:
-GA Travelcard for adults
-GA Travelcard Youth
-GA Travelcard for 25 year olds
-GA Travelcard for senior citizens
-GA Travelcard for disabled persons.
The second person can then purchase a GA Duo Partner.
More info here: Duo Partner GA Travelcard | SBB
Have a nice afternoon and reagrds
Eleonoras