When I was younger, my step-father's brother(technically my uncle) and I happily engaged in such activities willingly. He never penetrated me though- because I was a virgin then, and I guess he didn't want to risk anything. The best part was that I had known him nearly all my life, and had held a well-known crush on him.
All the while that we were doing things, he kept saying stuff like 'I love my girlfriend and that'll never change.' and 'If things were different it might have worked.' But what hurt the most was knowing that I could love him and hold him all I wanted, but he would never feel the same. I would desperatly try to be around him as much as possible, and it seemed like he didn't want anything to do with me. I wrote him letters that went unresponed, and attended stupid family gatherings in hope of catching a moment with him.
Sometimes when I think about it I tear up, but alot of time has passed since then, and I've found someone who loves and cares for me just as much as I do. But sometimes when he kisses me, it takes me back to being with my "uncle".

If your reading this, please contact me. I miss you more than words could express.