Missing the gene that creates jealousy. Hell, even had a gf once that got together with her ex now and again due to his extreme size that she would get a hankering for every month or so. Not like I own her nor was she doing anything on the sly. She treated me great and was an awesome and fun person. In left handed way her wanting a little variety "on the side" reflective of how sexual she was... that, of course, being her main squeeze, I benefitted from.
Yeah, so I workout like a wildman. I like to run and lift so do it for me. But also do it to be the best version of me I can be. If some guy much more endowed than me then not jealous, just a "good for him" thought if any thought.