Ben was one of Violet Baudelaire's friends back in the city.
Little of his life is known other than the fact he was a friend of Violet Baudelaire's. He gave her elevator blueprints for her birthday and although they were later destroyed in the fire, her knowledge of them assisted her with locating the kidnapped Quagmire triplets.
It is later stated that after the death of the Baudelaire parents, most of Violet's, Klaus's, and Sunny's friends had fallen by the wayside, meaning they stopped writing, calling, or stopping by to see them, which made them very lonely. It is possible that this is why Ben makes no appearance in the series.