A really cool feature available via Google is an archive of pictures from the files of Life Magazine. I have downloaded a couple here to show the five Marx Brothers out of costume in their later years. The first picture comes from Wikipedia Commons and shows the whole Marx family around 1913.
Groucho, Gummo, Minnie (mother), Zeppo, Frenchy (father), Chico and Harpo, at about the time of their act "Fun in Hi Skule" of 1913.
The Marx Brothers, --(Fore L-R) Harpo, Chico, Groucho and (Rear L-R) Zeppo and Gummo, standing outside together. Photo by Peter Stackpole, 1938
The Marx brothers (L to R) Harpo Marx, Zeppo Marx, Chico Marx, Groucho Marx, and Gummo Marx at Civic Playhouse for opening of "The Fifth Season" in which Chico stars. Photo by Allan Grant, 1957
"Duck Soup" in Ithaca, NY
4 hours ago