@Thirst_420 @vousmevoyez I have the feeling that their relationship is fine right now, since they both know how the other is and are not deceiving each other. It's not like the dude is twisted and she doesn't know. It's more like the dude is twisted since he loves his sister and would backstab anyone for it, not because it's in his nature to do so.
His nature actually seems pretty kind, since he does so much for a woman that never even notices his feelings.
So what if he ends up falling for our FL, someone that actually returns his feelings? Then we might see some positive changes in him.