Oh you poor thing! My girlfriend got two yorkie puppies WAY TOO YOUNG and tiny (she wouldn't listen to me
) and her little girl did the same thing- she would take her outside for 30-40 minutes and the second she brought her in, she would poo in either the kennel or x-pen, and then get it all over her.
She finally got better about it but I don't think she's completely trained yet. I don't even know what I would do, well, I do know I would be super skinny because I would be throwing up everytime I had to clean out the kennel.
I wish I had better advice for you! On the bright side of things, at least it's only ONE of them who's doing it! It could be five out of six
What if you took him outside by himself and totally ignored him until he did his business? Then make a huge deal? I really don't have any other ideas.