Complex sentence: He had married Catherine, eldest daughter of Oswald Leycester (another notable Cheshire family) in 1810: they had five children, including Owen Stanley, Arthur Penrhyn Stanley and Mary Stanley.
Split into simpler sentences: He had married Catherine, eldest daughter of Oswald Leycester (another notable Cheshire family) in 1810. They had five children, including Owen Stanley, Arthur Penrhyn Stanley and Mary Stanley.