How do I convince my parents to let my GSD into the house? Or is it not recommended?

I have an 8 month old GSD puppy, and I really want to let him in the house so that I can spend more time with him 24/7. However, my parents didn't agree with that idea and said that it's ridiculous to do so, for never have they heard of any big sized dog roaming around in the house. Plus, they fear that the dog would do its business on the marble tiles. Can someone give me ideas? Thanks.