Complex sentence: In 1926 Cain married Dorothea Grindrod, with whom he had two children: his son John Cain was born in 1931, when he was already nearly 50.
Split into simpler sentences: In 1926 Cain married Dorothea Grindrod, with whom he had two children. His son John Cain was born in 1931, when he was already nearly 50.