Complex sentence: Farmleigh was formerly one the the Dublin residences of the Guinness brewing family it was purchased from the Guinesses in the late 1990's and following extensive renovations is now the official Irish State Guest House.
Split into simpler sentences: Farmleigh was formerly one the the Dublin, Ireland, residences of the Guinness brewing family. It was purchased from the Guinesses in the late 1990's and, following extensive renovations, is now the official Irish State Guest House.