First, if it's just a stupid joke among peers, you can have a conversation with those involved about appropriate language and respect. Tell them it's not okay to use such vulgar terms in relation to your son.
Well, without more context, it's hard to say exactly. It could be that there is some sort of object or situation that has been misnamed or misrepresented as a 'huge cock'. Maybe your son has a large - sized item that someone is joking about in a very improper way. But we should always be cautious of using such vulgar language when referring to children.
This is rather inappropriate. However, if we consider it in a non - vulgar sense, perhaps in some fictional or symbolic stories, it could be a way to represent an over - exaggerated characteristic for the purpose of satire or to show an extreme in a character's physicality, but this is a very rare and odd concept in proper literature.
It could be a story about his pet rooster that is very large. Maybe it's the biggest rooster in the neighborhood and it has some interesting behaviors like crowing really loudly or being very protective of the other chickens.
Well, if not in a vulgar sense, 'huge cock' could potentially be a misnomer or a very strange way of referring to something large. Maybe it's a big rooster on the family farm that the stepmom has some sort of story related to. But this is a very odd and uncommonly used way to phrase it if not being inappropriate.
It's definitely not normal. Sharing stories related to private body parts in this way is not acceptable behavior. There are social and moral boundaries, and this kind of sharing violates those. It can make others uncomfortable and is not in line with proper social etiquette.
On the other hand, it could be negative. If it's about a large tool that he misuses or that causes some sort of disruption. For example, if he uses a really big hammer early in the morning and the noise disturbs everyone, then it would be a negative story.