Complex sentence: The eldest son born after the 1797 Lambeth marriage of the fifth Earl, Thomas Moreton FitzHardinge Berkeley, became on the Earl's death in 1810 "de jure" 6th Earl of Berkeley--however, he refused to claim his right to the earldom.
Split into simpler sentences: The eldest son born after the 1797 Lambeth marriage of the fifth Earl, Thomas Moreton FitzHardinge Berkeley, became on the Earl's death in 1810 "de jure" 6th Earl of Berkeley. However, he refused to claim his right to the earldom.