I thought I had heard years ago that Humphrey Borgart had been the Gerber baby. Urban legend, or am I just confused?
Another legend is that Maud drew/painted the Gerber baby. That's not true either, although Maud Bogart was a successful commercial artist.
Source: I've been a massive Bogart fan since high school, and Bogie's birthdate really was December 25. That wasn't made up by a movie studio trying to soften Bogie's image because of his frequent early appearances as a gangster.