I never got the impression that any of those three were at all interested in polyamory. Steve and Cosette seem to be happily monogamous, and Tortura seemed to be happy with the guy she was currently with (other than her perfectly sensible paranoia that the CIA was going to come along and try to use him against her).
I definitely got the impression that Cosette
was entirely terrified of Tortura. It looked like she could barely squeak out an "
o-okay" when Tortura threatened to feed her to the pigs. Can't say I blame her. Your boyfriend's ex shows up at your house, and you discover that she is - as Steve put it - "some crazy Russian chick with more scars than good sense", how would
you react?
And to save everyone else looking them up, the relevant strips for all of this are
1350 &
1406/
1408 (Steve & Tortura),
1918 (Steve talks about Cosette moving in),
2629 (it appears Cosette
has moved in), and
3428 (Tortura threatens Cosette). The only time we've seen Steve since then,
he was, in fact, eating cereal.
I feel like Jeph would have made a big deal out of it if Steve and Cosette got married, since Steve is one of Marten's best friends.