IIRC, when the company was formed, everyone got an equal split. They may have issued more shares when some other key people joined. But, when someone quit or was fired, they had to forfeit all shares (got paid out based on the companies revenue over the last year).

Eventually a bunch of people left and I think only two founders remained (Carmack and Carmack).

Since the stakes were reabsorbed, it makes sense why he ended up with 41%.

John Carmack slaved away writing super optimized ground breaking realtime 3d game engine code that created a multibillion dollar industry.

Adrian Carmack mostly took photographs of clay scultures (and in some cases actual plastic toys, in the case of the chainsaw and pistol used in the original Doom), and digitized them in Corel. Something any half-way decent art student could do (not to discount the iconic visual style of Commander Keen and Doom!)

It was Adrian who walked away with 41% of the >100 million dollars company!