It was in multiple games, multiple external Nintendo-approved sources, the TV shows, the movie, and in Miyamoto's own words. You can't just write all that off.
The movie even implicitly resolves the issue of Baby Mario and Luigi being seen in the Mushroom Kingdom -- their parents took them to Earth when they were young to escape the Koopas, which itself resolves the issue of Mario's apparent two mothers.
and
are obviously not the same person as
Albanomama is Mario and Luigi's Italian adoptive mother; Skinnymom is their biological Mushroom Kingdom human mother.
Where's the fun in putting together a Mario canon if you completely ignore the TV shows, the movie, the books, and the older or less popular games?