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Thanks a lot. It worked!

Thank you stefen, I have updated the post with preamble. There is not re-definition in the document class. I guess the problem might me in the loaded package. Thanks again!

While compiling following file, I am getting repeted chapter title before chpater heading. How can i slve that.
Main Code:
\documentclass[11pt,a4paper]{book}
\include{format}
\makeindex

\begin{document}
\pagestyle{empty}\pagenumbering{roman}
\tableofcontents%
\mainmatter %
\pagestyle{fancy ...