Complex sentence: They tell him she is to be married to the Earl of Marsden, which delights Aubrey, who requests to his guardian that he be present at the wedding, and also that he may have an audience with his sister.
Split into simpler sentences: They tell him she is to be married to the Earl of Marsden. This makes Aubrey quite happy, and he requests to his guardian that he be present at the wedding, and also that he may have an audience with his sister.