Yes, you should be able to add him as an AU to your CC. I assume this is the Chase Amazon CC, not the GE Amazon store card, which I am not familiar with. I added my DH as an AU to my Chase CC without problem. I think I did it online but you could just call the number on the back. Being added as an AU can help the AU's credit if their file is thin and the card has good history.
If it's the store card, you should still be able to add him as AU and have it appear on his CR.
Thank you both. It's the store card. We are trying to rebuild credit after a BK. I will add him and see if it appears on his report.