Complex sentence: The descendents of his grandson William de Moravia's descendents became Lords of Bothwell but changed their name to Moray (from the great province of Moray, once a local kingdom) by the end of the 13th century.
Split into simpler sentences: The descendents of his grandson William de Moravia's descendents became Lords of Bothwell. The name became more generally written simply as' Moray' (or variants), deriving from the great province of Moray, once a local kingdom, by the end of the 13th century.