I always imagined Red XIII to have a deep voice though he's supposed to be a teenager for his species.
I actually thought he had a deep voice back in the day, because Bugenhagen says he is very deep, but I realise now that that line referred to his personality.

Awww kids these days, can't look it up on that old final fantasy website, nope just google it on your phone. BACK IN MY DAY we had to bicker with people on internet message boards!
The password changes each time, though...

I love that you're doing this, Final Fantasy VII was so awesome when I did it the first time, so I can totally relate to what your kids are experiencing - and they're going through it without any previous experience (I was aware of some things, due to reading strategy guides long before even buying the game), and even then it was an awesome experience as the next scene happened. I'm sure it's really fun for them, hearing it in your storyteller style.