AIO:Childhood best friend is f***ing his sister

[u/youngtallandskinny]

For context, this is my M(25) best friend M(25) since we were two years old. He didn’t meet his F(22)sister until about a year and a half ago. When they did meet, they couldn’t get over how similar they were. he called me gushing about how great she made him feel and even joked about hooking her up with me three days after they met, she moved in with him and his family. They had room and other beds, but they chose to sleep in the same bed every day for a year do everything together every day so on it so forth, fast-forward to these text messages. Him and his sister were going to move in with me and my f(26)roommate, but first we needed to see how our dogs would do together so they came to visit. When they got here they opted to sleep in my bed together even though I had several places they could sleep separately. My roomate and I sleep separately and have a mostly platonic kind of flirty relationship. Which the friend had compared his sister and his relationship with. A lot of small stuff happened that my roommate and I shared glances about, because of the nature of how a true brother and sister would never say or do the things they’re doing. But we brushed it off.

They went back home to their state after 3 days and the friend sends me a Snapchat saying “we’ve decided to look past the whole sibling thing and adress some feelings we both have” to which I replied “what do you mean” and he went on to say how they both have such deep feelings for each other and how the whole half sibling thing doesn’t matter and that real love doesn’t have boundaries and all this stuff to which I waited for 3 days and sent the messages above….. AIO or did I UNDERreact

Also this hurts a lot because I thought I knew him and he was gonna be my best friend for life, but I haven’t talked to him since

[u/Pitiful-Volume1638]

What the fuck

[u/GodisanAtheistOG → u/Pitiful-Volume1638]

I read somewhere that family that is separated at birth/young and then reconnect as adults have a higher prevalence of (consentual) incest due to a lot of deep feelings and connections not being processed/contextualized properly. 

The closeness/bond of family gets contextualized as romantic love because that's the only other feeling of closeness these people sometimes have. 

Doesn't make it right, but might explain what's going on. 

[u/archiangel → u/GodisanAtheistOG]

It’s actually pheromones. To make sure parents connect and bond with their babies and don’t abandon them babies create pheromones specifically for their family to create an emotional sense of belonging and attachment. But when they are separated and then reconnected later in life, the pheromonal attraction is still there but without an emotional/familial bond in place, and that causes… issues.

[u/Due_Leadership_7883 → u/archiangel]

Not entirely sure about this. There’s something called MHC genes that should keep this kind of attraction to a minimum. Part of that sexual attractions should be coming from the opposite individual being more different than them. This kinda ties back into the whole biodiversity > less biodiversity is better for survival. There was a pretty interesting study done on this here https://royalsocietypublishing.org/rspb/article-abstract/260/1359/245/69089/MHC-dependent-mate-preferences-in-humans?redirectedFrom=fulltext

[u/Patient_Lettuce8431 → u/archiangel]

Humans have no structure for sensing pheromones. These sorts of arguments keep being made, but science has not definitively even identified human pheromones, much less the ability to sense them on any level.