My mother (LPR) lives with me in the US as a dependent. She applied for my 3 younger brothers who have their interviews in a few weeks. I am the financial sponsor for their visas. The list of interview documents they should bring with them includes proof of domicile for our mother. I am not sure what proof to submit because she does not have any of the documents listed on this page: https://travel.state.gov/content/travel/en/us-visas/immigrate/the-immigrant-visa-process/step-1-submit-a-petition/i-864-affidavit-faqs.html#aos18
She has a state ID, social security card, medical bills, and I have claimed her as a dependent on my tax returns for the past 5 years. Will these suffice as proof of domicile? I wrote a letter explaining she is fully dependent on me as part of the initial paperwork she submitted. Should I write another letter for my brothers to take to their interview?