I suspect that mutual pining is similar to my "I love you but we can't be together" trope. My two Forever OTPs are both these kind of pairings - they *have* been together in the past, and they both know that they both love each other, but for Reasons™ they can't stay together. See Dick/Babs from the DC comics and Starbuck/Apollo from Battlestar Galactica!

And yes, that perfectly in-sync mirroring is awesome!!