Orientation play is a wide ranging topic for erotic fiction. However for porn, there are really only two interesting ones: Forced Bi, and Lesbians Forced Straight. Forced Bi involves a guy being forced (by a woman) to do or fantasize about gay things.

Lesbians Forced Straight (which doesn’t really have a consistent name that I know of) involves a lesbian or a lesbian couple having sexual contact with a man, reluctantly or completely against their will.

This is technically a form of male domination. It feeds off of insecurities about lesbians. What guy hasn’t been actively or passively rejected by a hot girl who turned out to be a lesbian? What guy doesn’t have a hot lesbian friend he pines over and fantasizes about? (I’m pretty sure it’s not just me.)

The situations forcing the lesbian include the usual:

• Blackmail
• Mind control, hypnosis
• Cam girls get special request

And some things specific to lesbians:

• Caught having lesbian sex, but must keep it a secret (from parents)
• Want to have a baby, can’t afford artificial insemination
• Curious or miss cock, don’t tell my girlfriend
• Femdom lesbians need a human dildo
• Dom lesbian punishes sub partner
• My girlfriend has never experienced cock, can she try yours?

These all work okay combined with incest, but there are some ideas that work for it uniquely (perhaps I will write up scripts for them specifically):

• Letting dad/brother watch
• Your brother deserves a blowjob from you / to fuck you
• Punishing spy / panty thief

Key Points

The forced part is generally important. Therefore, her reluctance must be demonstrated in her demeanor and her dialogue. You might think that the artificial insemination concept would have little or no reluctance, but even then, she should be nervous, and perhaps overcompensating for her nervousness by smiling a lot.