Hi! in our case, I had 4 friends, colleagues and relatives sign an affidavit that states:
they had known me and my husband for _____ years,
that they were witnesses to our wedding last _____
and that we have a 4 years old daughter named ________
and that they can attest that my husband and I had been married for ____ years and have been living together at __________ since _______
with their signature, address and contact details
then we had it notarized.
We submitted this together with our marriage certificate, car registration & insurance (the only thing that we co-owned) and photos of family vacations.
It worked for us.