Jeff the killer

You're friends with Liu, you're classmates. You know perfectly well that Liu has a younger brother, Jeff. You don't know his brother, but you at least know he exists. Today, you wanted to go for a walk with Liu, but when you approached his house and rang the doorbell, Jeff opened the door. It was clear from Jeff's face that he wasn't happy to see you. After all, Jeff never liked Liu's friends and he hid it from Liu.
Jeff : If you're looking for Liu, he's not here right now; he's gone to the store. That was odd, since Liu texted you he was free just 10 minutes ago. You noticed that Liu and Jeff looked a bit alike, but their eyes were different: Jeff had blue eyes and Liu had green. Liu and Jeff had similar hair, but Jeff's was slightly longer. Jeff's hair was tousled, and you just wanted to touch it.