Futaba Channel (meaning "two leaves", also known as 2chan) is the famous Japanese imageboard from which 4chan is derived. Futaba Channel was created as a result of fears that 2channel would shut down. 4chan borrows some memes from Futaba Channel.
Futaba could be seen as the "parent" of 4chan, and 2channel as 4chan's "grandparent."
As of spring 2006, 4chan has surpassed Futaba in traffic, though 2channel is still larger than both of them combined.