He and I never discussed it but I guess she told him I knew. My wife knew, of course, I was encouraging her to take it to the next step with him beyond flirting.
Just the opposite sex, two people getting to know each other over time, the natural juices flowing, then flirting. I knew it was happening but I tried to stay out of it, act like I wasn't aware, I didn't want to mess it up.
While she was blowing me, I told her to show me how she sucked his cock and she did. When she was riding me so she could orgasm, I kept telling her to ride his cock, take it, etc. He emptied his balls in her. Just wonderful.