Under different circumstances I think Kouga and Inu Yasha could have been friends or at least tolerated each other. I started this story awhile ago and am still in the process of completing it. Enjoy.
Title: A Pup and a Cub
Characters: InuYasha, Kouga
Warnings: Eventually there will be a lime/lemon between Miroku and Sango. Also, this has evolved into a multi-chapter story.
Summary: Kaede is accidentally injured during a fight between Kouga and InuYasha. A visiting miko and childhood friend of Kaede's curses them by transforming them into children as punishment for their childish actions.