The Arrangement
It's a reasonable arrangement, and not even Kal comments.
Merina must marry an Atlantean noble, but her brother doesn't care when. Rex doubts he'll ever marry. He enjoys waking next to someone he's known forever, someone who recognizes all his scars both inside and out. He recognizes hers, too.
The rules are simple. Both can date as they please, with or without continuing the sex. Either can break it off with a word. No questions of the "Who" or "Why" variety. No talk of a future that can't be. No falling in love.
Rex has kept every rule but one.