He knew they would eventually notice something was different about him but he also didn't want them to treat him differently. Though judging from their reactions it was inevitable.
Seeing this Rui Yewan suddenly took a step forward and placed his hand on his shoulders reassuringly, "We know.... You are not the same as that monster." He could understand what Rui Fei was feeling right now. Imagine finding out that you had the predisposition to become as wicked as the person you hate the most.
A better way to explain this would be a child of a serial killer finding out they are predestined to follow in their parent's footsteps. The stress and anxiety that comes from that are hard to imagine especially when society already stigmatizes them for being the spawn of such a demon.
Rui Fei probably didn't want Ji Yao to find out which is why he lied to him. Rui Li smiled at her brother and said, "Don't worry brother, your secret is safe with us. Now cheer up."
