Not sure why you are seeing a change now, iCloud Photos has always synced photos with all devices that share the same Apple ID. That is how it has always worked to give you the same photos on all of your devices. It is possible either you or your husband did not have iCloud Photos turned on before. In that case, you would each have your photo library that would not be shared. If you are the primary and still want access to all of the photos using iCloud, they you may want to have him turn off "Sync this phone" and if he has room on his device, then a copy of all the photos will be saved there as well. If he does not have room, he can choose not to download them and you can airdrop any photo he wants. With that said, Apple still does not recommend family members share the same Apple ID.
You do have the option to have seperate Apple ID's and still share purchases or subscriptions by using Family Sharing. This Support Article will help you with that.
Make sure that each family member has a unique Apple ID - Apple Support
As seen in that article, Apple recommends that each family member should have their own Apple ID. If you do not want to share purchases or subscriptions, then you do not need to use the Family Sharing approach. He can start with a fresh Apple ID by creating a new one. He will have to have a different email address to use as that Apple ID. Then he will just need to sign out of the current Apple ID and sign in with the new one. Any apps that were downloaded with the previous Apple ID will no longer be able to be updated, so they should be deleted and then downloaded with the new Apple ID. If the app was purchased, you would need to pay for them again with the new Apple ID. Any content on your iPhone that he wants back on his, such as photos or contacts can be AirDropped to him.
How to create a new Apple ID - Apple Support
You have 3 choices:
- Shut off iCloud Photos on one of the devices. A couple of reasons why Apple does not recommend sharing the Apple ID is that it is possible that you may see each others messages if you use iMessage and have it set to receive by your ID. Also you may get each others Voicemails.
- Create new Apple ID and set up family sharing to share purchases and subscriptions.
- Create new Apple ID and do not use family sharing.