The story is told from Jared's POV. I think he's 13. Jensen is Jared's older brother Jeff's best friend and they go to college together. Jensen visits the Padaleckis and Jared has a crush on him. I remember a sort of first time scene between the Js that happened after some party, I think it was New Year's Eve. Also, although it may be my mind trying to trick me, I think Jensen visits them several times, and their relationship evolves.
I remember Jared being very outgoing and having a connection with Jensen, and Jensen liking spending time with Jared even though Jared was only 13.
I'd say it had over 13k words?
It was on Ao3 if that helps, but I couldn't find it there.
Sounds familiar? :)

And if you know any cool stories where Jared gets to know Jensen because of him being Jeff's friend then please share too :) especially if it's a less known one

Edit
FOUND, it was two different fics:
http://archiveofourown.org/works/4048531/chapters/9108706
http://archiveofourown.org/series/6542