Complex sentence: The frequency of hereditary rule was much less frequent during the Burji regime, but with rare exceptions, the Burji sultans were all linked to the regime's founder Barquq through blood or "mamluk" affiliation.
Split into simpler sentences: The frequency of hereditary rule was much less frequent during the Burji regime. Nonetheless, with rare exception, the Burji sultans were all linked to the regime's founder Barquq through blood or "mamluk" affiliation.