New York City has a new batch of firefighters, including a group following in the footsteps of their parents 18 years ago.  Of the 301 probationary firefighters who graduated Tuesday from the New York City Fire Department (FDNY) training academy, 13 are children of firefighters who died at the World Trade Center on Sept. 11, 2001.  Six are sons of firefighters or police officers who died of 9/11-related illnesses.