The first and most important point is that bisexual people are not always poly, and it is really not okay to assume a bisexual person will want to become the third in your couple.
I admit, some people might be bisexual and also interested in dating a couple. But you can’t ever assume that, and it’s not true for most bisexual people. They are usually monogamous.
The other thing about bisexuals is that if they make a long-term commitment to a person of one sex or the other, it doesn’t not mean that they have “chosen” that sex. I am married to a man. That does not mean that I am no longer attracted to women, and it does not mean that I like women less than men.
Being with a person of one sex does mean that your feelings for the other sex are invalidated. It just means that you fell in love with a person of a specific sex. It might be confusing for you, but it is confusing for us too.
Sometimes people ask which gender I was attracted to first, as though it matters.
For the record, it does not matter. The gender I felt attraction to first is not my “real” sexual orientation.
I was just over 10 years old when I first felt sexually attracted to anyone. Her name was Samantha. She was blonde, and she was outgoing and fun.
I didn’t understand at the time what the feelings were, just like how straight people don’t understand. Attraction in general manifest before a complete understanding of sexuality.
So, the fact that I stared out being attracted to women, and am still attracted to women, does not mean that I am a lesbian. It just means that my attraction to men manifested later.
Sexuality is different for everyone.
Gay people sometimes feel resentful that a bisexual can “go straight” and “pass” with heterosexuals (therefore avoiding being marginalized and subjugated by the world at large.) Not all gay people are like that, of course. Many of them are wonderful and nice. However many bisexuals say they have experienced resentment at the hands of gay friends, who think the person is being less than genuine about their sexual orientation because they sometimes date opposite gender partners.
Straight people sometimes fetishize bisexuals. They can think of them as sluts who will have sex with anyone. It is very common, for example, for a straight male to ask a female who is attarcted to women if they can watch, or if they can join in. The assumption is that a bisexual is into weird things and different kinds of sex with multiple partners.
However, bisexuals are not to be fetishized as sluts who want to sleep with everyone. They are mostly very normal people, and the vast majority are looking for a committed relationship with one sex or the other; not an orgy like you saw on Pornhub.com.
I know that to some of you it will seem like this doesn’t need explaining. I wish that were true. However, as a life-long bisexual, I have experienced all of these things first-hand, and so I can assure you that they are real.
I would ask both straight and gay people to understanding that being bisexual is just another sexual orientation. We are still people; just like you.