Tenant roommates having trouble

[Josh Gold]

Hello all!

I've got a situation that I can't find on the Forum and was hoping to get some feedback from professionals out there.  One tenant and his girlfriend reached out to me about their roommate (all have been renting from me for quite some time without issue) and asked if there was a way to basically kick the 3rd roommate out.  He's become lazy and doesn't really contribute to keeping the place clean and the tenant and his gf are trying to keep a nice house.  I'm definitely ok with the couple staying and the other roommate moving on but not sure if it is my place to get involved, even though they asked me.  The suggestion that they gave was to give them a 90 day notice to vacate then re-lease the unit to just the two of them.  Any thoughts here?  I'm in Newberg, Oregon, just FYI so landlord/tenant laws, though not as intense as Portland, are definitely Tenant favored.

Thank you in advance for any commentary you can/are willing to provide!