Complex sentence: Owain's daughter, Angharad, married Gruffudd ap Cynan, Prince of Gwynedd, and his son, Gronw, was the father of Christina, second wife of Owain Gwynedd.
Split into simpler sentences: Owain's daughter, Angharad, married Gruffudd ap Cynan, Prince of Gwynedd. His son, Gronw, was the father of Christina, second wife of Owain Gwynedd.