You walk in on an unexpected pairing

In the aftermath, a switch has seemed to flip with your wife.
She's more affectionate and open.

Likewise, your Sister-in-Law has been more approachable and friendly.

On Black Friday, a bunch of the family goes out to shop.

You, your wife and your Sister-in-Law end up staying in for various reasons.

Eventually, you finish checking on how your post-game betting results were and walk by the Room shared by your Brother and his new Wife.

You hear...noises.

The sounds of rubbing and...kissing?

You open the door and fin an unexpected sight!

Your Wife (in a sun dress) is sitting on the bed making out with your Sister-in-Law (in a tank top and shorts).

They hear the old door open and stop to look at you.

"I can explain," your wife says.
"She can," your brother's wife says.
"Alright...I'm interested. Lay it on me, sweetie."

Your wife blushes at the sweet talk, as does your brother's.

"I wanted to talk to her about...what happened. We share a unique connection, after all."
You nod in agreement.
"She told me how strong and assertive you were. How you didn't treat her like you were going to break her."

Is that how she thinks of your lovemaking? Really?

"In turn, I told her about how assertive and teaching your Dad was. He didn't have your...merchandise, but still did quite well."
Hearing your prude wife refer to your dick out loud (let alone in mixed company) is a new experience.
Also it felt good to hear that you were bigger.

"She started talking about new experiences, got closer to me and then, well, started to kiss me."
Your Sister-in-Law nods, explaining that she started the whole action.

"I see. I appreciate the honesty," you say with a smile, "Now..."