I took advantage of my stepson's girlfriend's exhaustion to have sex with him

A couple of days ago, my stepson and his girlfriend came to my house. They were very tired from a long trip. My stepson was fucking her hard, and she was moaning with pleasure. I couldn't resist and decided to take advantage of the situation. I went into the bedroom, where they were fucking, and I started sucking his big cock. The girl was too tired to resist my advances, and she just let me do whatever I wanted. My stepson was very happy to have sex with his stepmom, and he fucked her hard and deep. I enjoyed every moment of it, and I can't wait to do it again.