My living situation a couple years ago was a huge mess, but it was - for a short while at least - close enough to what's described here that I think it's worth responding. The best bit is that it wasn't even two alloaros!
Before I realised I was aro, I was in a (supposedly) romantic relationship, and not doing a very good job of it, for obvious reasons. My girlfriend had moved in with me, not so much because we were following the relationship escalator - things definitely had not progressed to that point, it was waaaaaay too soon - but just because I had space and she didn't have other options. Long story short, we broke up - turns out I didn't want to be in a romantic relationship, for some unknowable reason??? - and she still didn't have options. We worked things out, because we had to, and she ended up in an open or possibly polyamorous relationship with another person, while cohabiting and maintaining fwb with me.
This still wasn't sustainable, because she wanted to move somewhere that wouldn't make her actual SO and I super awkward for being in the same room, but yeah the non-sustainable part was the accommodation rather than the relationships. We're still fwb, and I don't think either of us sees it working out super long term but it's still working just fine for the moment.
So yeah it might have only lasted a couple months but technically fits all the boxes: cohabiting, sexual partners that had to change things for a reason other than catching feels.
Serial sleep-kicker here, sorry not sorry, it's not something I have control over!