Hello!
My boyfriend and I aren't married but have been together for 11 years. I think NZIS just want proof that yours is a genuine stable marriage.
All we sent as proof was our tenancy agreement (we were renting in the UK) which showed we took the house 6 years ago, then we also sent a recently dated letter from our landlord to show we were still in the house together. We also sent a joint bank account statement from when we opened the account a few years ago, and our most recent statement. And that was sufficient.
Hope that helps - sorry can't help with the daughter situation.
Clare
