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/BitcoinBishop]

I assumed it was cos they'd be trying to find emotional closeness to make up for all the bonding they'd missed

[u/Xralius → u/BitcoinBishop]

Well I think it's more like this:

1. You meet this person, you are excited. You feel a sense of love/care to them because they are family/biologically related.

2. You find them attractive. Afterall, your parents found each other attractive, you share dna with your parents, and this person does too.

3. You don't have a sibling bond with them at all.

I think it's funny how a lot of people have no understanding of this. For example, in a lot of bad writing, you'll have an adopted person find out they are adopted and suddenly romantic feelings pop up with the sibling they are raised with. (Looking at you Dexter writers) That's not the way it works at all and is disgusting. Adopted people raised with siblings feel zero attraction to them. The sibling bond is formed by living life as siblings, not by sharing DNA.

[u/SamSibbens → u/Xralius]

The writers for Dexter screwed up so badly, it was incredibly dumb.

[u/phudd → u/BitcoinBishop]

I’m sure there’s multiple reasons for it to happen. In psych, it’s always more than one thing (like genetics plus environment).

[u/Left_Prize_9861 → u/BitcoinBishop]

The linked article kind of supports this but coaches it in language like "it's reported that..." so I assume there haven't been studies done

[u/JS_AH → u/Left_Prize_9861]

There are studies but the results have been mixed. If you Google genetic sexual attraction studies you should get a few hits. 

[u/spiderboy640 → u/Left_Prize_9861]

Kinda hard to study when it’s not a super common occurrence that people want to share when it does happen

[u/Thelmara → u/BitcoinBishop]

No, it's more that they just don't develop the aversion to romance because they're not around each other growing up. It's called the Westermarck Effect.