Complex sentence: Although Dorien had several flings with younger men, Luke Horton was her most frequent lover and she appeared to genuinely love him, from the first series until he left Dorien for a younger woman in the second series.
Split into simpler sentences: Although Dorien had several flings with younger men, Luke Horton, was her most frequent lover and she appeared to genuinely love him. From the first series until he left Dorien for a younger woman in the second series.