Complex sentence: His mother Catherine Mulvihill's parents, Maria Marsh and Thomas Mulvihill, were from County Westmeath, Ireland, and his father, Alfred E. Smith, was the son of Italian-German immigrants.
Split into simpler sentences: His mother Catherine Mulvihill's parents, Maria Marsh and Thomas Mulvihill, were from County Westmeath, Ireland,. The elder Alfred was the son of Italian-German immigrants.