Does anyone know what Malcom In The Middle's family last name is? They always use everyone's first names, but I haven't ever heard them say their last name. If someone could help me out that would be awesome! Thanks!!

Their last name is Wilkerson.

Thanks first of all! Just wondering how you know the last name is Wilkerson? Did I miss a key episode?

I found out from TVTome. In the notes for the pilot it says:

A scene that was script, but never filmed-Malcolm's last name is revealed as Wilkerson. Nor has it ever been revealed where the family lives.

It was The Wilkersons!!!