Yeah you can leave that blank but I still put my parents names, just not their SSN. Read the instructions, they come with the form.
__________________
Case type: Arrived O'hare Airport at age of 12, Visa Overstay
Compiled by: Self,
Sent: Aug 27 2012 to Chicago lockbox.
Confirmation: August 31st
Biometrics: Sept 21 2012
Approved: 10/16/2012
EAD: 10/18/2012,
Applied for SSN: 10/25/2012
SSN Arrived: 11/3/2012
ID:11/7/2012
DL: 11/15/2012