When the kids have grown up into attractive adults, the sexiness is compounded. Two guys overbrimming with erotic energy, yet with a nurturing, domestic bond. And if you get some sausage sightings, you can see if the son inherited his father's penis.
Not too many fathers and adult sons would be willing to see each other nude in the United States, where we have a Puritan hangup about nudity. But in Europe it's commonplace for fathers and sons to strip down together, go to saunas or the beach together, drink beer togther.
I've never had any erotic interest in my own father. The familial bond precludes erotic desire. But I fantasized about my friends' dads when I was in junior high and high school. A lot.
More after the break.
A book on gay folklore claimed that a major urban legend in gay communities was accidentally having sex with your father, a sort of reverse-Oedipus myth keying into anxieties over gay men's "failure" to become fathers themselves.
I never heard such a legend, and many gay men are fathers. They have children from early hetero relationships, they engage in artificial insemination, they adopt.
I don't think many guys are actually attracted to their own fathers. I get called "Daddy" a lot, but that seems to be just slang for an older guy.
I've never been with a father and son at the same time. I don't think I would want to -- it would make me a little squeamish. My friend Alan did, but the father and son didn't actually interact with each other.
I'm pretty sure these aren't his actual sons.
Probably a swim coach, not a dad.
See also: Alan Hooks Up with a Father and Son