we have a dog moving in with us that belongs to our grandson that refuses to leave the?

Ok excuse me but unless this dog is three times the size of you all NO dog can refuse to leave the house. The dog isn't the problem THEY are. Not your dog not YOUR responsibility to train and I would not be letting this animal into my home without knowing they are putting forth the consistent effort to train their animal.

Try puppy pads. If I were you I would make sure the dog is going out to use the poo and pee at least every 2hrs.

WE just got a 4month old English Setter who wasnt trained. We got him 1 week ago and he hasnt had a accident yet. We take him out every 2 hrs. Also take him on 2 walks everyday. His last outside potty break is at 1030pm. He goes the rest of the night until 7am without having a accident.

GoodLuck

You said the dog is only 3, which might make it easier to retrain him. Just be patient and take him out for short periods of time so he will start to feel comfortable. I think with enough encouragement and patience, the dog will be able to feel comfortable going outside to do his "business".