Nooo! You can't split up Johnny and Yosaku! ;_; dethorats is right though, this IS the kind of thing than could concievably happen in One Piece.
It's funny, today I finally got around to actually buying (as opposed to reading online '~') vol 5 of the manga, and I was just reading the bit where Johnny thinks Yosaku is dying and thinking how sad if would be if one of them DID die... and you've confirmed it ;___;