My brother's wife is my best friend since kinder-garden and before I had a serious relationship with his sister we liked to party a lot and we enjoyed the most sharing girlfriends in a threesome or foursome. Since I started dated his sister we never did it again but the idea was always in my mind and I guess in his too. After two years away with my wife, we returned to our home town and we invited my wife's sister for a commemoration dinner. With all the drinking and pot things went the way they used to go when we were younger. My wife liked the idea but only because she wanted to try DP and she allowed her brother only to enter her backdoor.