He was never accused by anyone, there is no evidence that he ever engaged in inappropriate activity with children, and those who knew him say he gave no indication of having such feelings, but...
If you mean Jean M. Barrie of the steamer-trunk mystery, it's not clear if she is. There was a woman by that name who identified herself as a "close relative of" James Barrie, but he had no children,...
Yes, he married actress Mary Ansell in 1894. The marriage was lacking in intimacy (so to speak), and she began an affair in 1908. Sir James divorced her the following year.