Jessica, I totally agree with browniesmom........I'm new here, first day, but I have 5 little rescue yorkies, (we rescued and placed 125 over the last 2 years), and we have found that they do teach each other. We take them out all at the same time and highly praise each one when they do what they're suppose to do. We keep a lead on the new ones at night (in bed) and it helps teach them to stay until we grab ahold of it and lead them out. I also use pads just on the kitchen floor and they really have taught
each other where to go.
Good luck on your new little one and as with kids, you'll have more than enough love and time for both of them.