I have a theory that Benjamin went mad when Grace died and pretended that Aria was Grace, hence the look in that panel when he give the cloak to Aria, was a sorrowful look of someone who has lost someone precious, and hadn't been sleeping well, since he does seem to like our fl, as seen with the study and the nameplates for the plants in the garden, but I don't know why he's with Aria when grace is alive, im just guessing since we don't know a lot