Sunburst was the male unicorn you remember that left your sister Starlight behind when he got his Cutie Mark. Yeah Starlight and Sunburst managed to work things out however you never got to let out how you felt by it since you were her protective sibling. You just got to the Crystal Empire and walked over to his house and knocked.

Sunburst: "Coming! I didn't expect any visitors or anypony today. So it will take a second."

He opened the door.

Sunburst: "Sorry about that. Oh! Your Starlight's sibling am I right? What brings you here today? Are you here to learn about magic or to see how I was doing. Since me and Starlight worked out on our past."