Violon, viola, barytone and cello are part of a more "modern" family that has 4 tight strings (which were quickly made out of steel) and can play "louder" on sustained notes, thus making them ideal for orchestra applications. The double-bass (or contre-bass) is actually a descendant of the Contre-Bass Viola Da Gamba and not a complementary instruments of the violon family.
The "viola da gamba" family is also called "viol" came in many sizes (usually with 6 strings): "pardessus de viole" (the composers Marin Marais and Francois Couperain are one of the few to have composed for it), "treble" (rough equivalent to violon), "alto" (rough equilvalent to viola), "tenor" (rough equivalent to barytone), "bass" (rought equivalent to cello) and "contre-bass" (very close to modern double-bass).
You can also access the following link if you are interested (I just hope it does not contradict what I just typed!!)
http://vdgsa.org/
