Step-sister's compromise to help me befriend her brother

As I've been struggling to make friends, my step-sister stepped in to offer her help. She suggested a compromise - in exchange for some alone time with her, she'd introduce me to her brother and help me break the ice. I was hesitant at first, but her tantalizing offer was too much to resist. Unbeknownst to her, her brother had been listening in on our conversation. As soon as she left the room, he pounced on me, eager to take advantage of our little agreement. What followed was a wild encounter, leaving me completely drained. Little did I know, this was just the beginning. When my step-sister returned, she was more than willing to keep our little secret and join in on the fun. Now, whenever the urge strikes, we indulge in steamy threesomes, our taboo relationship only deepening with each encounter.