How do I do an evection to someone who isn't a renter or a tenant and refuses to leave?

They are either a owner, renter or tenant.

It is that you just don't know what to call them. If they are living there, even if not paying rent, they are still a renter or tenant, just a non paying one.

If they are your wife or husband, that is different.

So tell us what is the relationship here and what they are

ANY question on law needs to include your general locale as laws vary by area.

They are either an owner, leasee, resident. Or guest. The guest label applies only to very short term occupants. If they are an owner you can't evict. If they are on the lease, then the landlord has to evict. If they are a resident, then the landlord or leasee has to evict.

Please give us more details about the situation so we can advise.