on a separate sheet of paper, provide any additional details of your current relationship that you believe would help to prove your relationship is genuine and continuing.
Examples if you didn't mention somewhere else in the form:
Something about how you're buying a new home, or adding kids, etc.
If you have anything that proves you're together, like joint accounts, joint insurance (life insurance beneficiary is spouse), health coverage stuff, etc.
If you joined clubs or activities together, etc.