Complex sentence: Genet married Sir Thomas Fitzwilliam and had four children, including Richard, the heir; their grandchildren included Thomas FitzWilliam, 1st Viscount FitzWilliam.
Split into simpler sentences: Genet married Sir Thomas Fitzwilliam and had four children, including Richard, the heir. Their grandchildren included Thomas FitzWilliam, 1st Viscount FitzWilliam.