Legally, you can evict them. Morally, is this what you really want to do? You seem more concerned about their well being to me but unsure how to approach the family problem and possible mental well being issue of your relative.
The answers on this discussion board are general in nature and NOT intended as legal advice. Responding to questions does not constitute an attorney-client relationship. Always see a lawyer about your individual situation.
You should consult with a landlord tenant attorney to get legal help with an unlawful detainer action. If you want the tenant out, legal steps and paperwork need to get filed.
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