Complex sentence: Details about Sherlock Holmes's life, outside of the adventures of the books, are few and far between in Conan Doyle's original stories; nevertheless, incidental details about his early life and extended families portray a loose biographical picture of the detective.
Split into simpler sentences: Details about Sherlock Holmes's life, except for the adventures in the books, are few and far between in Conan Doyle's original stories. Nevertheless, mentions of his early life and extended families paint a loose biographical picture of the detective.