We’ve all got our very own sex fantasies, which play out in our heads to make us hope that, one day, they’ll come true. From having sex with a MILF, to getting down and dirty with the hot teacher in detention, a lot of our sex fantasies come from the X-rated vids that we tend to watch. But are there more “normal” ones than others?

That’s a loaded question, because, especially these days, there are so many sexual things that people are into that it’s hard to just bracket everyone into a certain category. For example, one of my friends was describing how he gets asked by an older married couple if he wants to take part in a threesome, with the husband and wife even sending dirty videos of them having sex to try to entice him. The couple have three kids, and, according to my buddy, have even sent videos of the husband giving oral sex to another guy while his wife watched. This isn’t necessarily “normal,” if you ask a lot of people. But, guess what, it’s not weird either.

As sex as become less taboo to talk about, so, too, have sex fantasies. And because one size doesn’t fit all for everyone, there shouldn’t be anything “weird” out there — as long as it’s safe and consensual.

However, one sex fantasy that still tends to fall into the bad category is a boyfriend thinking about what sex would be like with his girlfriend’s friends. We’ve all thought it. Hopefully, we haven’t followed through on it. But, since it’s one of those sex fantasies that has both crossed our mind and is a popular search on X-rated sites, we decided to break down if it’s ever OK to do.

Is sex with a girlfriend’s friend really one of the most popular sex fantasies?

As you might imagine, yep, fantasizing about sex with a girlfriend’s friend is definitely one of the popular sex fantasies out there; so don’t think you’re in the minority if it’s ever crossed your mind.

In fact, according to lehmiller.com – who did a study on more than 4,000 Americans for the book Tell Me What You Want — a lot of people admitted that they find themselves attracted to a friend or sibling of their significant other. But, more so, it was heterosexual men who said that they had these sex fantasies. Take a look at some of the results of the study.

Source: lehmiller.com

As the table above shows, heterosexual men were the highest percentage of people who fantasized about sex with a partner’s best friend, but non-heterosexual men weren’t too far behind. This is telling, as men of all different sexualities seem to be intrigued by this kind of sex fantasy.

Why do we fantasize about sex with our girlfriend’s friends?

This is an interesting question, because we can’t just get into our own minds and figure out why we like or dislike anything. For instance, how is it that you love ketchup on a hot dog, but not mustard on a hot dog? Or why can you eat scrambled eggs, but dislike eggs when they’re sunnyside up? The mind is a powerful muscle, guys.

The aforementioned from lehmiller.com helps to explain why sex with a partner’s friend might be one of the top sex fantasies, though, with the simple theory of men having more taboo sex fantasies than women do. Take a look at the explanation below.

So how do we explain this pattern of results? It may have something to do with a finding I discuss in Tell Me What You Want, which is that men have more taboo sex fantasies in general than women. For some reason, men are just more turned on by the idea of doing things they’ve been told they can’t or shouldn’t do. This may stem—in part—from the fact that men tend to be higher in sensation-seeking tendencies, so perhaps they’re more drawn to taboos because it provides an extra thrill.

Additionally, it’s typically believed that women desire more passion and emotional chemistry than men do while having sex, which may also explain why more guys fantasize about sex with a friend of his girlfriend.

If this is one of my sex fantasies, do I tell our girlfriend?

It’s up to you how you want to handle it, but, personally speaking, no, you shouldn’t tell your girlfriend that you’re having sex fantasies about her best friend. That can lead to more problems than you both want or need in the relationship, and it can cause tension or doubt in your partner’s mind if she becomes insecure about any potential feelings you have towards her best friend.

For instance, if you plan on going out in a group one night, any mention of your girlfriend’s best friend joining may trigger something in your lady, which can ruin the entire night. Plus, while being honest on open is important in a relationship, you don’t need to tell each other everything, so it’s OK to keep this to yourself — even if something in your girlfriend triggers her to ask you.

If it becomes a bigger problem than just a fantasy, though, and you begin to feel more attracted to her best friend than your girlfriend, that’s when you need to assess the situation and see if it’s better to end the relationship. It’s best to be honest with those feelings rather than cheat or manipulate your girlfriend by flirting or sleeping with her best friend at some point down the road.

Is it OK that one of my sex fantasies is sex with my girlfriend’s friend?

To answer the question, yes, it’s completely OK to have sex fantasies about having sex with your girlfriend’s friends. As the lehmiller.com chart shows above, a whopping 58 percent of heterosexual men and 52 percent of non-heterosexual men already do this, so it’s not as if you’re cheating because you happen to find another girl attractive — even if it is your girlfriend’s friend.

It’s important to differentiate fantasy vs. reality when it comes to your sex fantasies, and thinking about sex with your girlfriend’s friends doesn’t mean you’re doubting the relationship. As it turns out, this fantasy might just be more of a novelty than anything else, similar to sex with multiple people or sex on an airplane, where few people actually act out on the fantasy.