I saw the tread on the couple who swaped in laws....
We have been doing that for years.. the wife & her sister husband swap on visit, ( we live 2 states away) ...
Its something to behold! Her sister & hubby are not open swingers at all, but limit their activities to just us.
Tha general routine on visits is : first night, the home being visited wife stays home w/ the others hubby,, and the others go to a hotel for the night. Completely private time to do as pleased w/o the spouse around. It works very well, and the hotel couple comes home @ noon the next day.
On the 2nd or 3rd day, everyone plays together at home as a 4 sum. I found that her sister is much wilder w/ me alone, then when we all get together.. my wife said the same about her husband.?? Remember they only swing w/ us, so they probably get a little reserved in front of each other.. except for the obvious 2 cocks at once when we are all together.
The wives don't go down on each other as sister, but they do alot of touchy / feely to stimulate each other or when one of them are getting their 2 cocks at once, they will touchy / feely tits, ass, pussy to help things along.
Her sister has a spectacular set of tits, as my wife is small chested... so for me its really nice to get my hands on my sis-in-laws tits.
So thats how it works for us... pic of those spectacular tits.