Complex sentence: Weasels are mammals forming the genus "Mustela" of the Mustelidae family which includes least weasels, European polecats, stoats, ferrets and European minks.
Split into simpler sentences: Weasels are mammals forming the genus "Mustela" of the Mustelidae family. The genus includes the least weasels, European polecats, stoats, ferrets and European minks.