Complex sentence: He married Henriette-Louise Colbert, the second daughter of Colbert in 1671, thereby becoming the brother-in-law of Charles Honoré d'Albert, duc de Luynes.
Split into simpler sentences: He married Henriette-Louise Colbert, the second daughter of Colbert in 1671. So he became the brother-in-law of Charles Honoré d'Albert, duc de Luynes.