Living in a new place with just my wife, we were just about to seriously start trying for a baby when my sister forcefully moved in for school. It would be fine if it was just living together, but my sister seems to have a thing for me and is seducing me relentlessly. She keeps coming at me every day, stopping our family planning! At first, I resisted strongly, but I'm slowly being drawn to my cute and sexy sister, who's even more so than my wife... Now, the sperm I can produce during sex with my wife is as thin as water! I'm sorry, wife!