<human>: Can you give me the gist of the text in a nutshell?

My friend and his wife have been together since freshman year of college. They are both Hindus and said they were saving themselves for marriage. My older brother on the other hand has been a huge womanizer, he isn't the stereotypical jock, he is a lot like a good looking nerdy guy. Me and him used to be close before he left for college (we both go to the same State School). And besides Holidays we don't really talk much. 

My friend and his wife got married this summer in India and are actually having their American Wedding in a couple of months. This Thanksgiving I invited my friend and his wife over to our house in Thanksgiving. And I just saw that when my friend's wife saw my brother, her face just got suck almost. I saw throughout the time we were there she was just looking at the ground.

I asked my brother if he knew this girl and he told me that they were in the same class that they used to fuck. I asked him if he was sure, because she has told everyone that she is a virgin. And he was sure, and the other thing was this was happening during the time my friend and his wife were together. 

I didn't say anything then, because I didn't want to ruin anyone's Thanksgiving but now what do I do? My friend and I have been good friends, he was my first roommate and I know that if I was in his situation I would want to know. The thing is, I am worried if he would even believe me, since he loves his wife with all of his heart. I want my friend to know what's going on, but I don't want to ruin anything. My older brother had no idea that she was in a relationship.
<bot>: found out during Thanksgiving that my close friend's wife cheated on him with my older brother. I want to tell my friend, but I am worried that his wife, will tell him that I am making things up.