Complex sentence: He moved back to Galloway at eighteen months old, and the area formed a basis for his early fiction, and in the 1940s moved to North Wales, where his son the writer Andrew McNeillie was born.
Split into simpler sentences: He moved back to Galloway at 18 months old, and the area formed a basis for his early fiction. In the 1940s he moved to North Wales, where his son, the writer Andrew McNeillie, was born.