Question: What German social reformer's brother was a German pioneer of aviation who became known as the "flying man"?
Sentence (from "Gustav Lilienthal"): Gustav Lilienthal (October 9, 1849 – February 1, 1933) was a German social reformer, a pioneer in building and construction technology (Prefabricated buildings), inventor of different Construction sets (e. g. Anchor Stone Blocks) and involved in the pioneering work of his brother, Otto Lilienthal in aviation.
Relevant evidence: Yes