It seems the two guys have been best friends and neighbours since they were on diapers and he ended up marriyng his best friend's younger sister. The husband said they always shared everything between them and now he wanted to share his wife too, like the guys he sees on the internet letting others fuck their wives while they record it on video, and his best friend had to be the first, the only "but" was he's her wifes's brother and she was a bit unconfortable at first.