It's not a family tree - a) that would be too large and b) it assumes games mate and produce offspring. This is a family line, showing all Mario games, by generation, with their siblings.
The thing is so super-huge you should probably just go directly to it or download it to magnify it for yourself. But it covers all 130 games featuring Mario or any permutation of the Italian pipefitter/construction worker, beginning with Donkey Kong, including Wrecking Crew and Mario Teaches Typing (1 and 2) right on down through Super Mario Galaxy. The groupings seem to be by platform type and/or genre.
Mario Family Line [Limit Break]