Haha taeny has dated. I assume taeny broke up last year. Remember the sudden influx of Heechul on taeyeon's instagram? That time there is also a rumor stating that Kangin went to visit snsd in their dressing room and they staged a couple's break up. It was also that time when fans feel that taeny had a fight because they don't seem to appreciate each other's presence during that time? Heechul's presence is like taeyeon is running away from fany and choose to use Heelchul as a distraction? It was around sept-oct and taeyeon's IG photos were not 'bright'. Then taeny came back which I guess fany gave taeyeon a chance. Then during early Nov, taeyeon posted 'If you really love someone you have to learn how to let go'. Then soon after, taeny came back again. I guess maybe taeyeon thought she had fany back again. Soon after but around late dec-early jan, khun came along and fany started dating him.

Let me make a conclusion on the theory. It may sound delusional but it is based on the rumors + facts.

Taeny dated back then but around late sept or early oct, taeny had issues and they went on and off then broke up during Nov. Soon, taeny came back and taeyeon mistook the signals. Maybe fany just wants to make things bearable since they are still colleagues and dorm-mates. But deep down fany knew taeyeon mistook the signals. Soon, fany started dating khun and ALL the members EXCEPT taeyeon knows. She knows that it will hurt taeyeon but she remembered the no secrets between members rule so she decided to approach taeyeon and taeyeon finally realises the reality and cried all night. She sang be alright and posted it on instagram and youtube where fans thought that taeyeon is trying to comfort sones. Then on 17th jan do you remember taeyeon went to the beach alone to think? It was also on THAT day sunny and fany was caught going to a restaurant and met Khun. It may be a date and sunny's presence is just a cover up. Taeyeon knew about the date so it explains taeyeon's depressed feelings. I guess she sang breath and set me free with all those feelings. I was actually wondering if taeyeon experienced break up then because it felt so sad and real. Now I know why. Then along the way taeyeon tried to put up a facade. We all know how taeyeon is like. She is one who do not want people to worry about her so by putting up a facade in front of fany and sones can cover up what she really feels. BUT during the variety shows, taeyeon often zoned out and she only laughs when the host or someone interacted with her. Remember when the host ask fany about ideal man during guerilla date and taeyeon rolled her eyes? I guess Nichkhun came up to her mind. Then taeyeon kept up the 'I'm okay' facade till now. During the latest taeny instagram photo, taeyeon seem distant with fany and taeyeon's 'sun' where it was just in a circle, her caption was 'Something I drew while I wasn't thinking about anything', an interpretation is that she is frustrated deep down and she can't step out of her circle of thoughts. Taeyeon also seldom smile on her instagram recently. The latest mixxo photoshoot, taeyeon don't smile as brightly when she hangs her arm on fany. Like she is cherishing that moment but yet feel awkward and sad? Taeyeon also said on healing camp that she is lonely. Back then, I was thinking if fany was with her, how can she feel lonely? Now I know why too. She is also afraid that sones would leave her. I guess she is afraid to lose sones after losing fany because sones is her only dependent.