Should a 13 year old boy sleep shirtless?

Well, honey, at 13 years old, that boy is probably going through puberty and discovering all sorts of changes in his body. If he's comfortable sleeping shirtless and it's not causing any issues, then go for it. Just make sure he's in a safe and appropriate environment. And hey, if he starts feeling awkward or self-conscious, there's always the option of throwing on a comfy t-shirt.