Definitely not appropriate. Family relationships are based on love, respect, and appropriate boundaries. This kind of description involves extremely abnormal and unethical behavior. It is not something that should be part of any story or real - life situation. We should uphold positive family values and ethical standards.
Once upon a time, there was a little boy. He loved his mom more than anything. Every day when his mom came home from work, he would run to her and give her a big hug. He would also pick little flowers from the garden and present them to his mom. He said those flowers were as beautiful as her.
It's completely inappropriate. A mother should be a role model in propriety. Such stories are not only improper in terms of content but also may make the friend's son feel uncomfortable or even exposed to inappropriate information. It's much better to engage in conversations about things like sports achievements, cultural events, or recent interesting news.
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.
Yes, it is clearly an inappropriate interest. Such a topic is private and should not be a subject of interest among people in this relationship. It violates the normal boundaries of friendship and marriage.
There are also some illustrated children's books where a big rooster is the main character. The story might revolve around the rooster's adventures because of its size. It could be that it has trouble fitting into the chicken coop or has to find special ways to interact with the smaller animals due to its larger stature. This can teach children about differences in size and how to adapt.
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.