Complex sentence: When William died on 23 November 1890, Emma became regent for her underage daughter, Wilhelmina, the late king's only surviving child until Wilhelmina's eighteenth birthday on 31 August 1898.
Split into simpler sentences: When William died on 23 November 1890, Emma became regent for her underaged daughter, Wilhelmina, the late king's only surviving child. She would remain Queen regent until Wilhelmina's eighteenth birthday on 31 August 1898.