For the life of me I can't remember where I read this great story. It's a slow-burn multi-part story that was posted to some forum that might have had a cuckold type of theme. Story centers on a youg man who's stepdad is a macho muscle brute. I think he owns a gym or is a personal trainer. The stepdad is the exact opposite of the son, and the mom, who are both meek and mild. At the end (spoiler alert?) it turns out that the alpha stepdad was originally a "bull" in the mom and original dad's relationship... The stepson ends up discovering he is also more of an alpha. It's not a pure "muscle" fiction story but there are muscle/gym and dominance themes. Any help would be appreciated.