Hear me out, Lucanis and Rook were MARRIED before the whole fake death thing. Rook goes off on a grief fuelled rampage leading to the Antaam thing, Viago smuggles them outta Treviso to go adventure with Varric and Harding so they don't get whacked for ruining the Crow operation.
At Neve's request reaches out to the Crows to ask about someone who could help, grandma-in-law Caterina be like yeah.. Your husband is actually alive, pls go get him then you can kill the gods and be forgiven for your screw up.
Rook is a frickin MESS. Lucanis is a frickin MESS. Spite kinda sorta knows Rook from the get go because Lucanis thought about them so much in the Ossuary.
They spend the whole game dealing with their trauma, realising their spouse might not be the same person they married and deciding.. You know what, you might have a demon sharing your body and you might be a bit different but you're still my hubby Lucanis. Likewise Rook might have gained a new nickname, might have lost some of that polish their twin brother Viago instilled into them but.. It's still my loving Rook, always sees the best in me and does some mean spellwork with a blade.
And ofc they have to kill the gods, deal with Solas and work on house training their pet Spite demon.