Family Won't Leave Property I Just Bought. How To Evict?

I am about to close on some property that I bought from my uncle, but my cousin has lived there for 3 years rent free. The agreement was that she and her family would leave once I bought the place but now they don't feel like it.
They never had a rental agreement or lease. Just a family arrangement. The uncle wanted to sell and the cousin couldn't afford to buy it, so I bought it for myself instead.
How do I go about the process to evict? I don't know what category they fall under: tenant, holdover tenant, or maybe even squatters. This is in Salem OR.
Any help would be appreciated! Thank you
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