Complex sentence: In the aftermath, Nest's brother Gruffydd was spirited into Ireland; their brother Hywel was injured, and captured by Arnulf de Montgomery; the fate of Nest and her mother is unknown.
Split into simpler sentences: In the aftermath, Nest's brother Gruffydd was spirited into Ireland; her brother Hywel was injured, and captured by Arnulf de Montgomery. The immediate fate of Nest and her mother is unknown.