DynamoDB has no foreign keys. This is a NoSQL database that does not support such relational data. There is no data integrity between tables, so this behavior is not built-in. If you want to have this behavior, you will have to model your datastore in DynamoDB differently.
From the FAQ explaining that a non- relational database:
While Amazon DynamoDB solves major database problems of scalability, management, performance, and reliability, it does not have all the functionality of a relational database. It does not support complex relational queries (such as joins) or complex transactions. If your workload requires this feature, or you are looking for compatibility with an existing relational engine, you might want to run the relational engine on Amazon RDS or Amazon EC2. While relational databases provide robust features and functionality, scaling a workload outside of a single instance of a relational database is very complex and requires considerable time and experience.