Q: Problem with multiple themes deploy in Magento 2 When I execute CLI command: php bin/magento setup:static-content:deploy. It always has only 4 steps themes, but now I have multiple duplicate themes while running the command.
frontend/Magento/blank/en_US            2631/2631           ============================ 100%   < 1 sec          
frontend/Magento/blank/en_US            2631/2631           ============================ 100%   < 1 sec          
adminhtml/Magento/backend/en_US         2709/2709           ============================ 100%   0                frontend/Magento/blank/en_US            2631/2631           ============================ 100%   < 1 sec          
adminhtml/Magento/backend/en_US         2709/2709           ============================ 100%   0                frontend/Magento/blank/en_US            2631/2631           ============================ 100%   < 1 sec          
adminhtml/Magento/backend/en_US         2709/2709           ============================ 100%   0                frontend/Magento/blank/en_US            2631/2631           ============================ 100%   < 1 sec          
adminhtml/Magento/backend/en_US         2709/2709           ============================ 100%   0                frontend/Magento/blank/en_US            2631/2631           ============================ 100%   < 1 sec          
adminhtml/Magento/backend/en_US         2709/2709           ============================ 100%   0                
frontend/Magento/blank/en_US            2631/2631           ============================ 100%   < 1 sec          
adminhtml/Magento/backend/en_US         2709/2709           ============================ 100%   0                
frontend/Magento/luma/en_US             2648/2648           ============================ 100%   1 sec            
frontend/Meigee/sirena/en_US            2925/2925           ============================ 100%   12 secs     

I will be grateful for the hint! Why my themes are duplicated?

A: If you have created theme with any parent theme which is mentioned in app/design/frontend/Vendor/theme/theme.xml in  node.
So when you do setup:static-content:deploy, first it will do deploy for parent theme and then for child theme.
