After years of flirting, 45 year old [M]arried husband cheated with friends’ wife who’s in our close group of friends

We’ve known this couple for about 7 years. Gone out together as couples more time than I can remember & always considered them good but not great friends. Been to parties together, have tons of mutual friends, etc. His wife and I have always had a friendly flirting thing going on which was a little bit of a turn on but I never thought anything of it. Every once in a while when we were drunk she’d kiss me goodbye on the mouth and hold the kiss a little longer, or she’d make a joke about how big she thought my cock was (I’m tall), or how sexy it was that I kept in good shape – and looking back I realized I was just blind to what was very obvious flirting.

Last week I went over to their place to pick some stuff up. He was out of town visiting family so it was just her home alone on a Thursday afternoon. Gave each other a big hug and a kiss – which is how we normally greet each other, but once again she held the hug a little longer, pulling me really close and saying how good it was to see me. We went in and cracked open a beer and sat outside. Well one beer turned into two, I texted my wife to say I was gonna hang out for a bit longer and help her with a project – and then we pulled out a bottle of tequila.