Talking raunchily with a friend about (fictional) dad-son incest and YEAH.
I've long circled around the notion that Bruno and his twin sons are... closer than most parental relationships. (Bruno is their uncle, biologically). I've only written direct sexual contact between Bruno and Kristian once, with Kris giving Bruno oral.
But the reverse?
Specifically, Kristian feeling somewhat deflated about being circumcised; Bruno engaging in some intensely erotic worship of his son's junk, getting uncharacteristically Into It and really laying it on thick. Eventually cumming on Kris' hooves virtually hands-free.