In the "Romantic Mystery AU" from Hesowars, the matsus all have different names from the get-go and seem to have different families. However in the in-game event's story it's revealed that they are actually brothers, they were just separated somehow.
Osomatsu is Ozo, a taxi driver
Karamatsu is Karatsugu, a fledgling reporter
Choromatsu is Chorosuke, who lives in a Japanese-style mansion and does flower arranging
Ichimatsu is Hajime, the son of a librarian
Jyushimatsu is Toshio, but I still don't get what he even does
Todomatsu is Takashi, the son of a coffee shop owner
From what I can gather of the barely-translated material, it's a bit like a Japanese Twin Peaks with its own potentially-supernatural quirks. But because I can't fuckin read, it makes the lack of information on Toshio even creepier. He can seemingly teleport and and be in two places at once, freaky stuff like that, but I just don't know why. I assume there's chock-loads of references in the sprite animations too which fly over my head.