Hi,
The way we've described it would be that the Application Family would be applications that are related but function independently. Whereas the composite is a combination of independent / disparate applications that are formed to provide a larger application.
e.g. MS Office might be through of an Application Family (Word, Excel, etc)
A Data warehouse implementation of an Oracle database, some ETL tooling might be a Composite.
Application Family is a Vendor view or suite of the Applications
Composite is your own Company "name" of the Application set
Just just my interpretation / usage anyway.
Alex