It was a oneshot and the boys were in the Hummel/Hudson house with the family out to a, football game, I think. Anyway, lap sex happens with Kurt wearing a skirt and uh oh, Burt, Carole and Finn all walk in with Kurt and Blaine in the middle of, well, you know.
That's the gist of it and I'm dying to read it again and pass it along to a bestie. If anyone knows which fic I'm talking about, I would be forever grateful! Thanks in advance.
*Found in the comments