Are there any renters unions in your area? Getting the tenant involved with them might help them legally or practically. In the UK, we have Acorn which do a mixture of direct action (ie literally blocking Landlords from accessing the property) and supporting tenants with navigating the legal system and understanding their (somewhat limited) rights as renters.
If there's something comparable in your local area, perhaps approach them with the consent of the tenant? If there's not then perhaps there's similarly minded people which you can help to start organise and bring into the fold?
This isn't a terrible idea in general, but I wouldn't start practicing my revolutionary organising against my own family. I suppose it depends on what they might be able to offer. If they could help with the negotiating that I mentioned above…?