[x] Members or not

I'm about to enter the album Personality Crisis by The Bear Quartet and I don't know if I should include Björn Olsson and Carl Olsson as members or not. This is what the official website says:

"During the recording of Personality Crisis, Carl Olsson (synthesizers, guitar and screaming) and Björn Olsson (guitar, hammond organ and backing vocals) sort of joins the band, they play on every song on the album and are with us during the following tour."
[www.thebearquartet.com] http://www.thebearquartet.com/?page_id=6

The liner notes says: "bears: jari haapalainen, peter nouttaniemi, jejo perkovic, mattias alkberg; cubs: björn olsson, carl olsson"

AMG lists Björn Olsson as adjunct member while Swedish Wikipedia calls them "temporary members".

So are they members enough to be listed here?

I'd be inclined to say no purely because the Quartet already has its 4 members, but having said that I'm pretty sure there's already a precedent somewhere in the db for a quartet with more than 4 members or a quintet with more than 5 or something.

But anyway I'd argue that "sort of" joining a band isn't the same as *actually* joining.

Well, they have had five permanent members for at least ten years now so the fact that they call themselves a quartet shouldn't matter. It's just a name and doesn't really mean anything in this case.

Any other opinions on this?

edit: I now noticed that the liner notes also says "arranged by The Bear Quartet, Björn Olsson and Carl Olsson" which would imply they were not members of the band.

The album is now in the queue.