Midget Gerbils?

[Chris Kornicks]

Um...is it possible to get like a mini-gerbil?  Cause out of this litter of 4 that were born about 6 weeks ago or so, there was one little guy that my parents thought was younger then the rest.  But I know it wasn't.  So now, he chills in the cage with his Mom, and Aunt/Older Sister, and 3 (4 wk. old pups)...but the pups are almost as big as him....