We always jokingly flirt with each other and what not.
But he's started rubbing my back and once he feels my bra strap he'd play with it, not exactly undoing it, just putting his fingers under whilst twisting and pulling it (whilst I'm still wearing a shirt, not going to be just wearing underwear around him of course!)
Then he would move his hand round to the front to my breast, no groping just has his hand lying on it. My breasts aren't massive like so many girls my age.
I would be sitting on his lap (I've always sat on his lap since we were little, so it's not out of the norm for us but the following is) sitting across sideways and to keep me from falling he'd have his hands under my legs and bum. Whilst in the middle of talking, he moved his hand (the one on my bum) to my 'opening' and slightly tightened his grip on my ass and this made me jump as his fingers were in deeper and I know he is doing this on purpose because I told him off and to move his hand but he still left his fingers there. I don't know whether he did this to tease me as he enjoyed watching me jump and scream out for his own entertainment or if he found it alluring for whatever reason. (but then again, he wasn't exactly laughing :S)