Complex sentence: His elder brother Sabahattin is a well known writer and his younger sister Mualla one of the first architect working in restauration, and is well known for her work at the Topkapı palace in Istanbul, in the Harem section.
Split into simpler sentences: His elder brother Sabahattin is a well known writer and his younger sister Mualla, one of the first architect working in restauration. She is well known for her work at the Topkapı palace in Istanbul, in the Harem section.