The feature of Global/Shared Communities would allow you to share any of your community with other sub-accounts in your account. By making the community global you provide whole access to that community to the account you share with, making it easier for you to work with your team.
To set up a Global/Shared Community:
Go to: Login >> Communities >> Select/Hover Over the lock icon
Click on the Lock icon that says "Permission" on hovering.
Now, check the check box next to the user you wish to share the community with and click on Save Changes
This feature is available with the following license :