I was 19 then
Uncle Jim and Auntie Tess lived on a farm in Western Australia. I grew up in Sydney and had only met them once before when I was about ten. Now at 19 and more independent, I wanted to see the rest of the country and wrote to them asking if it was ok to come over and visit. They wrote back saying they would be delighted.
I hitched a ride out to where their property met the main road and walked the remaining half mile to their homestead, set back and well hidden by trees, as it got pretty windy out there at times. There was no sign of anyone when I opened the main gate leading into their front garden, so I guessed they would be either indoors or around the back. I pressed the doorbell and even knocked once or twice, but there was no reply. So walked around the back. No one there either. They told me there was a creek downhill at the back, so I headed there.
When I got a bit nearer I suddenly saw them, stretched out on towels, sunning themselves on the grass with an Esky of beer beside them. Then I realized Jim was fully naked and Tess had only her panties on. I was looking down on them from the hill, so they hadn't seen or heard me coming. I didn't know what to do, but just watching them made my penis began to swell with excitement. I decided that the longer I waited, the worse it would be, so came down and called out to them.
They both sat up suddenly and looked round, Tess covering her breasts with her hands. Jim grinned and said they hadn't expected me to arrive so early, apologizing for catching me unaware. He got up to shake hands, not making any attempt to get dressed, and his semi-erect penis was very noticeable. No one at home was a nudist and I felt a bit embarrassed to be shaking hands like this, especially as it was my uncle, but it felt exciting too in a funny kind of way. Tess had wrapped a towel around her by now, saying she hoped they hadn't shocked me, and giving me a little peck on the cheek. I didn't want them to see the bulge in my jeans.
Jim said they often stripped off here and asked me if I preferred them to get dressed. I replied no that was ok, as matter of factly as I could, hoping Tess wouldn't notice my looking at the crotch of her panties. So I put my rucksack down and sat next to them. As we talked, Tess decided it was safe to allow her towel to fall. For a woman in her fifties she still had quite a good figure, though a bit plump. I felt she knew I was looking at her, but trying to hide it. She gently suggested I might like take off my shirt and get some West Australian sun on my pale skin.
After my long trip, it felt good to do that. Jim poured me a cold beer, staying naked. After another couple of beers we became more candid. Jim asked me what I thought of Tess's body and she retaliated by scolding him and grabbing him by his penis. When she finally let go of it, Jim's erection was bigger than ever, but strangely I just felt happy that this couple were willing to share this bit of intimate horseplay with me. With the hint of a smile, Tess suggested I strip too, so I went down to my briefs and lay down on a spare towel she had brought.
Just as I did so, the head of my aroused penis popped out through the fly and Jim laughed, saying he could see the dickybird now. Tess told him to behave himself, then, looking at each of us in turn, she finished her beer, rose to her feet and stepped out of her panties, announcing 'You next' to me.
Naturally my penis sprung up as soon as it was free. Tess looked at it and asked if she could touch it. How could I say no? She rubbed some sun cream on her hands and gave the tube to Jim, who unashamedly began to masturbate. Then Tess bent forward, her breasts swinging, and began to caress me there too. With hardly any warning, I erupted with the longest and most powerful orgasm I had ever had in my life, on the blanket, the grass and Tess, while she held my penis with one hand and put the other around me. Jim grunted, ejaculating like a voyeur, before slipping his hand between Tess's legs and making her joy complete.
There were no secrets between us after that. The week I spent with Jim and Tess was one of the most wonderful times of my life.