How can I pre-assign a total number of columns in RDLC matrix table, with or without data?

How can I manage to display or let the matrix table display a total number of 11 rows. with or without data coming from the database..

my example:

• TableName: sibling.
• Entities: SiblingName , DOB, and a reference to the employee table

An employee entered only six siblings in the system. Now when it's time to display the report under rdlc.

How can I manage to make the matrix table display a total number of 11 rows even if the result from the dataset is only 6?