Flying Lemur

They aren't lemurs, they can't fly, but they're the greatest mammalian gliders on earth and they might be your cousin. 

Bibliography: https://docs.google.com/document/d/1tYVDiQix_0cqwVwzGhDW7oS2QjyBR9V6TAJ7FCj_yiE/edit?usp=sharing