About 12 months ago my boyfriends brother came to stay over as he was doing some work locally. He took us both out for a meal and drinks after. When we got back to our place we were all worse for wear. My boyfriend went straight to bed leaving me alone with his very attractive brother and a bottle of wine. We continued drink some more and chatted. Some how the conversation changed and got a bit flirty and we ended up talking about penis size. I don't know how. He reckoned he was bigger than his bro. Seizing the opportunity I asked him to prove it. With a small amount of coaxing he soon dropped his pants. I felt my pulse racing and before I knew his flacid, yet rather impressive cock was hard...and in my mouth. Somehow this progressed to amazing full sex on the sofa. We have never repeated this but I wish we could. He has never even mentioned it in passing.His girlfiend is a lucky woman as he is quite a bit bigger than my boyfriend aswell.