I didn't think it was possible to have multiple shared iCloud+ accounts in Family Sharing. Yes, an individual can stay with their own plan if they do not want to be part of a shared group.
Unless you are actually talking about two family groups...?
Have a look at Share iCloud+ with your family - Apple Support
where Apple says things such as:
"If a family member is already paying for their own iCloud+ plan, they can choose to switch to your plan or keep their own and still remain part of the family. When they switch to the shared family plan, they get a refund for the remainder of their personal plan. They can't keep their current plan and use the shared family plan at the same time." Share iCloud+ with your family - Apple Support
"Switch from your personal iCloud+ plan to your family plan
When you share iCloud+, any family members using the free 5GB plan are added to your family plan automatically.
If a family member is already paying for their own iCloud+ plan, they can choose to switch to your plan or keep their own and still remain part of the family. When they switch to the shared family plan, they get a refund for the remainder of their personal plan. They can't keep their current plan and use the shared family plan at the same time."
If you truly are just a single family group and your husband's plan has enough storage for all of you then you can cancel your subscription and everybody will automatically be covered by his.
If necessary for your husband, click on the link to learn how to switch to a different subscription plan on an iPhone, iPad, Mac, PC, AppleTV, or online --> How to switch to a different subscription plan - Apple Support