Let's start counting the number of times when: they're about to reconcile, but one or both of them get hate-mind-controlled. And neither one of them seem to have made any effort at trying to stop the mind control from happening again. And MC never tries to explain things to his sister. Like "Yo, I was mind controlled. And I only became a vampire after I lost to the vampire queen." It's just two speech bubbles, just do it!