Part 4 of Form I-751, Petition to Remove Conditions on Residence, is called “Information About the U.S. Citizen or Lawful Permanent Resident Spouse. If Filing as a Child Separately, Information About the U.S. Citizen or Lawful Permanent Resident Stepparent Through Whom You Gained Your Conditional Residence”.
First, in Form I-751 Part 4 you should choose your relationship type and tick the box “spouse or former spouse” or “parent’s spouse or former spouse”. Then you must provide the following information: full name, date of birth, U.S. Social Security Number (if any), A-Number (if any), and physical address of the corresponding person.