I can't really help you with your problem, but it sounds like your friend didn't continue to work with the potty training. I've always had Chows, which very rarely do you have to do house training.
I don't mean to be "rude" or anything like that, but since you have 3 dogs, 3 kids, and from what I understand one of the females had a litter, so you have at least 2 females, since this puppy is from a previous litter. There are WAY too many dogs and cats in this world and not enough homes, there are MILLIONS of dogs and cats that are put to death yearly. Are you a "recognized" breeder? If not, I would urge you to seriously consider getting all your dogs spayed or neutered.