I'm sorry to hear of your loss.
You can transfer either of them into a new return. You just can't transfer them both into the same return, as you can't prepare the return of a deceased person with someone else.
When you pick a coupled return to transfer, it will ask if there have been any changes, including if one of them have passed away. Then it will ask which of the two you want to transfer. You can choose one first, and then later, when you start the second return, you can choose the other.
This FAQ has more information regarding preparing returns for the deceased: https://turbotax.community.intuit.ca/community/product-information/help/can-i-prepare-a-return-with-...
