Complex sentence: Beatrice's paternal grandparents were Boniface I, Marquess of Montferrat and his first wife Helena del Bosco; her maternal grandparents were Marquess Boniface of Clavesana, Count of Cortemiglia and his wife who is unnamed Medieval Lands.
Split into simpler sentences: Beatrice's paternal grandparents were Boniface I, Marquess of Montferrat and his first wife Helena del Bosco. Her maternal grandparents were Marquess Boniface of Clavesana, Count of Cortemiglia and his wife who is unnamed Medieval Lands.