The only printed interpretation of this I can recall was in one of the "Preseason Softball Guides" published by NFHS a few years ago. I keep those in a file at home and might have it, but I'm not home right now. This is something that high school umpires should know and be aware of.
I would check with the umpires BEFORE the game, just to make sure they're going to say it's okay and before it could possibly become an issue. It should be fine...but you might want to have a back-up glove in the bag "just in case".
On the "same two numbers" thing...The uniform rules do specifically say that two players on a team may not wear the same number. But there really isn't much of a penalty involved if they do.
The first option is to correct the issue- just give one of the kids a different jersey. There is no further penalty involved.
If the issue cannot be corrected, umpires are directed to let both kids play anyway, without penalty. We are then to report the problem to OHSAA and they may follow-up with the school.
The official stance is that we want to promote participation for student athletes and they don't want to deny that opportunity based on something like a technical violation of the uniform rules- something that the player may have absolutely no control over.
That is actually the same thought process behind allowing a glove or mitt at any position- participation. They do not want to deny a player the chance to participate for lack of an expensive, specialized piece of equipment (like a catcher's mitt of first base mitt).