It’s not that they’ve forgotten their partners, it’s that they need each other. They are from different universes, but there’s still a connection, an undeniable attraction between them both. They’re not meant to replace what was loss, they’re meant to cope, to help them move past their trauma.

Their respective partners will never forget them, and will always carry scars on their souls from their abrupt parting. Axe was only a handful of years from dying outright from the state of his soul, Frisk was growing more and more ill every passing day. Together, though, they can finally begin to heal.

Ruby and Cobalt can even see that – though Cobalt takes a little more time getting to that conclusion. They are both dead and gone, and nothing can bring either of them back, so it only makes sense that they would want their partners to be happy and healthy without them – what else could they possibly ask of them? To die miserable and alone and in pain? They would never want that for them. Never.