Complex sentence: Her paternal grandparents were John Gordon, Lord Gordon and Margaret Stewart, illegitimate daughter of King James IV by his mistress Margaret Drummond, and her maternal grandparents were Robert Keith, Master of Marischal and Lady Elizabeth Douglas.
Split into simpler sentences: Her paternal grandparents were John Gordon, Lord Gordon and Margaret Stewart, illegitimate daughter of King James IV by his mistress Margaret Drummond. Her maternal grandparents were Robert Keith, Master of Marischal and Lady Elizabeth Douglas.