With the power of Ctrl+F and skim-reading, I failed to find the proof you wanted, @Gustavos. Sumia/Cynthia and Cordelia/Panne do involve them, but never name them.
While Kieran/Marcia comes close, I don't Marcia ever has the same impact. I think all of her supports that aren't Tanith/Marcia place the spotlight on the other character.