I get the feeling my Mom stepped out on my Dad from time to time.  I don't know if they were swingers, or whether she got some action on the side.  I do remember trying really hard to convince our family doctor that it was possible to get an STD from a toilet seat.  I don't know what she did to convince him to agree, but eventually he did.  As a side note, the same doctor delivered my wife and I about 2 years apart.  She continued seeing him until he made her change into a robe at 16 or so, and didn't bother to leave the room.