I went on holiday with my mate some years ago and we went into a self-catering flat with a sun bathing flat roof which was not overlooked.
We went up there every day and it was red hot. It was not long before he said he was taking off his shorts and would sunbathe in the buff. Eventually I did the same.
I noticed that his cock was about the same size as mine, about four inches when not erect, and seemed to erect sometimes and not others. He did not wank it.
He suggested that I put the suncream on him, and of course this had to include his cock. He started to erect and got quite big. Soon a spurt of cum came from his cock.
He did the same for me and then we had to clean up and sleep. Needless to say, this was not the last time!