Penny's Nephew

This unnamed boy is the nephew of Penny and possibly her brother which means that he's the possibly the son of their sister and possibly her shot husband. He has never appeared on the show, but has been mentioned a couple of times. It was revealed in Season 2 that he is 13 years old and in that same season, it was his birthday and Penny had help from Leonard trying to find him a comic he may like while visiting the comic book store.