RuneScape Classic Wiki
The main RuneScape Wiki has an article on: Billy Rehnison
The Old School RuneScape Wiki also has an article on Billy Rehnison.

Billy Rehnison is a NPC present during Plague City quest. He lives in West Ardougne.

His parents are Martha and Ted Rehnison, and his sister is Milli Rehnison.

No dialogue

While this NPC has a talk option when clicked the player gets the message "Billy is not interested in talking"