how many wives and children had the inspector had?

The inspector had had three wives, but they were all dead. From all of those wives, he had a total of twenty children. Many of those children had also died as well. This information can be found in the 17th paragraph of the story (the page number will differ depending on what version you have; however, the paragraphs will be the same). "He had been the husband of three wives, all long since dead; the father of twenty children, most of whom, at every age of childhood or maturity, had likewise returned to dust."