This experience happened to me a few years ago and it ended up being a couple that I got to 'join' about once a month over a 6 month period. They were pretty hardcore swingers and I think I learnt some good skills (particularly from the husband on pleasuring women).
This is what I wrote at the time just after the first time we met.
Last Friday night I had a threesome with a couple that I met online. A friend of mine recommended this couple as good fun. I spoke to them online before I arrived here and they seemed really keen and also rather experienced.
Friday night came along, I met them at a bar in town after dinner. Lots of photos were exchanged beforehand and they looked like their photos. I told them I was bi and they said that the husband is 'open minded'. After just one drink we were getting along fine and the wife asked if maybe we should head back to their place for another drink. It sounded good to me as I was getting a hardon in my jeans and black speedo already.
Their house was only a 5 minute walk from the bar.
When we walked in the husband went to the kitchen to make some drinks and the wife pushed me down onto the couch and we started making out. Our lips (and tongues) were locked until the husband came back with our drinks.
At this point the husband sat on the couch next to me and his wife got off my lap.
"Well Dave -- you told us that you like bikinis and speedos. How about you guys get down to your speedos and I'll go put on a bikini...."
While the wife left the husband and I did what we were told, we stripped down and it turns out we were both wearing a black speedo under our jeans (I had told them I'd be wearing speedos under my jeans before hand).
I was hard as a rock from making out with the wife and the husband was slowly getting there. It was pretty hot sitting on the couch next to a married guy, both in speedos, rubbing our cocks through the lycra waiting for his wife to join us.
So the husband and I are sitting on the couch both wearing black speedos. I'm hard as a rock from making out with the wife and we are both sitting there rubbing our cocks through our speedos. It doesn't take long until the wife returns. All she is wearing is a white bikini. She is petite, nice medium sized titties, shaved all over and brunette.
She notices straight away that I'm harder than her husband and getting on her knees between his legs starts rubbing the front of his speedo. First with her hands, then with her mouth.
After watching this amazingly hot sight, I decide that I should look after the wife. I need to cool down a little bit as well. I get off the couch and lying on my back on the ground, I put my head between her legs, pulled her bikini aside and tasted her moist pussy. My attention to the wife's pussy was met with a groan of pleasure from the wife and she started to grind her pussy on my face. I assumed the husbands cock was free of his speedo and wife was sucking hard on it.
After a little while husband told me that I could fuck his wife from behind if I wanted to. I was still super horny but I had cooled down a little bit and thought that I wouldn't blow my load after two strokes so I grabbed a condom and got on my knees behind the wife. Sure enough husbands speedo was pulled down and wife was sucking away on his now very hard cock. Wife's pussy was well and truly wet from the attention my tongue had given it over the previous five minutes and my cock slid in easily and the groaning coming from wife's cock filled mouth with every thrust of my cock indicated that she was enjoying having a cock in both ends.
Both husband and I were starting to get really hot and I know I was keen to hold off for a little while.
Thankfully husband had the same idea and suggested that we move upstairs into the bedroom.
So the three of us put our genitals back into our swimwear. Took a deep breath and moved up stairs...
Round two saw us move from the couch to the bed. The three of us were chatting casually, the wife was between husband and myself and all six of our hands were slowly exploring each other.
I was grateful for cooling down a little bit.
Conversation turned sexual of course. Turns out this couple are as open sexually as I was lead to believe. Turns out the weekend before, after a night out on the town the wife got talking to three Aussie guys outside a pub. The husband arrived and invited the three guys (who were 100% straight) if they wanted to come back to their home and fuck his wife. All three of them thought that sounded like a great idea and the wife was fucked by the guys one at a time on the couch. Then the three Aussie guys went home.
I thought this was pretty hot and by the time they had finished detailing this story I was hard as a rock and ready to go again.
The wife noticed just how much my cock was straining in the black lycra of my speedos and she suggested that we all get naked. It took about ten seconds for husband and I to get out of our speedos and for the wife to get her out of her white bikini.
This time the wife got her lips wrapped around my rock hard cock. The husband started to move behind here in a similar position to what we had enjoyed on the couch but the wife stopped him and I moved around into a sixty-nine position and told the husband to start fucking her.
This is my favourite threesome position. I get to eat some pussy, my cock is being sucked and I can play with the guys cock and in particular his balls.
I was licking the wife's clit as the husband slowly inserted his rock hard cock into her pussy. That distracted the wife from sucking my cock as she muffled a groan of pleasure from between my legs.
After a few strokes of husbands cock in the wife, I started playing with his balls with my right hand. It is a little tricky licking pussy when there is a big hard cock thrusting in and out of it and over the next couple of minutes I turned my attention from the wife's pussy to the husbands balls. He had mentioned in our online conversations that he didn't have any interest in being fucked by a guy so I didn't venture to start playing with his arsehole.
The husband was enjoying the attention I was giving his balls so much that he was moaning and telling me to suck his balls This wife thought this was pretty hot and started talking dirty telling husband to fuck her harder while I suck his balls.
Things were getting really hot now and husband and wife were both getting very vocal.
The husband was getting closer and closer and when the husbands balls tensed up I knew he was about to cum. He unloaded into his wife's pussy and my chin was getting covered in pussy juice and cum.
I got myself out from under the wife before I was drowned in sexual juices but before the husband had even pulled his cock out of her pussy, she and I were making out as she enjoyed the taste of her and her husband.
I was pretty keen to start fucking her but the wife had something else in mind. While the husband grabbed a towel and cleaned up a little bit, the wife moved south and starting giving my cock some serious attention. When the husband returned from the bathroom the wife told him that since I had sucked his balls, the least he could do was to suck my cock in return. The husband wasn't super keen on this and was happy to start eating the wife out again but she insisted he join her in working on my cock.
The husband had a bit of a slow start just licking my cock and holding my ball. But with some urging from me and his wife the husband finally put the head of my cock between his lips and started sucking.
Looking down at this view was really hot. The husband with my cock in his mouth, the wife with one hand on his head keeping it on my cock and her other hand was rubbing my balls.
All of a sudden I was really close to cumming. I was moaning louder and loader and telling the husband to keep sucking.
Then I felt that deep surge and told them I was about to cum. The husband didn't want my cum in his mouth and pulled off my cock but his wife jumped in there and sucked me dry. Then while I was still huffing and puffing I saw that the wife was kissing the husband so I guess he did get a taste of my cum after all.