Our threesomes

my husband and I have enjoyed threesomes now for quite some time, has anyone else done the same, if so some questions 1/ how did you first talk to each other about doing this or any other sexual thing involving other couples/single people 2/ did you have rules about with whom you should get in with 3/ being a wife, I have enjoyed the attention and the sax tremendously, have or did you 4/ my husband is a voyeur, he loves it in a MFM. however I'm not all the way into FMF, can explain if required