Complex sentence: He had several children, of whom at least two, John and Rachel, survived to adulthood: his descendants were mostly associated with Skibereen, and usually spelt the family name Gosnell or Gosling.
Split into simpler sentences: He had several children, of whom at least two, John and Rachel, survived to adulthood. His descendants were mostly associated with Skibereen, and usually spelt the family name Gosnell or Gosling.