My puppy is acting worse?

I have a 10 week old Italian Mastiff/Hound mix. For the first three weeks we had him he was doing great and making great progress. His housebreaking was going really well, he would have one, maybe two accidents a day in the house. He was biting and nipping less and less and he was listening when given commands. Suddenly last week he started peeing all over the place and his biting is getting worse. He's not allowed in the kitchen and he wasn't even going in there after being told not to a few times, but now we can't keep him out. Im not sure but I don't think it helps that my girlfriends little brother and sister let him do whatever he wants even after we've told them to correct wrong behavior.