I am naked in my house all the time. I have my 13 yo nephew living with me. After a brief explanation, I was back to my usual ways. In about 3 days, he was in his birthday suit too. Its healthy and natural to be naked and no problem with being naked with him. Good that he sees a mature male naked and know and understand what puberty is about to do to him.
Being 13, he is a little shy about himself at times, but is learning that I am not concerned if he becomes "excited" as this is a natural thing to happen. Its all part of being a male. I get them too and I am not embarassed by it.
Nobody reading this should ever be upset with being naked at home with family.