Complex sentence: At Jefferson's direction, he was buried on the grounds, an area now designated as the Monticello Cemetery, which is owned by the Monticello Association, a lineage society of his descendants through Martha Wayles Skelton Jefferson.
Split into simpler sentences: At Jefferson's direction, he was buried on the grounds, in an area now designated as the Monticello Cemetery. The cementery is owned by the Monticello Association, a lineage society of his descendants through Martha Wayles Skelton Jefferson.