My older brother and his wife, who live with me at my parents' house, are worried about infertility. They desperately want a child, so they asked me to provide them with their sperm! I never thought I'd be able to have sex with my beautiful sister-in-law, with my brother's approval! I was happy about this lucky turn of events, but to my surprise, we had sex under my brother's supervision! I was honestly disappointed that the sex felt like a chore, with only my sperm in mind... but later, when my brother wasn't around, my sister-in-law, who was actually feeling it more than I expected, invited me for some unofficial lovey-dovey sex that was super exciting!