This has been a fascinating subject I've had to address a number of times.
I'm a genuine bisexual male. I've played in these settings and have enjoyed fucking the wife and then fucking the husband as the wife watches or even participates in some kind. I love getting oral from another man as much as I love having a woman giving me oral. I don't know how this came to be, it just is. I have an attraction to both men and women and find no problems fucking both. But I will say that encounters such as these have been rare, as some men are not willing to try certain things sexually because they find them "gay" or not exactly what they're comfortable with.