After a pregnancy scare, Lois convinces Peter to get a vasectomy. Just in case they wanted to have more children, Peter goes to a sperm bank to preserve his sperm. But in a mishap, Peter breaks all the jars and fills them up with his own sperm. Thus, creating Stewie's half-brother and rival Bertram when a lesbian couple decide they want a baby. Meanwhile, Stewie takes his place as king of the playground but when Betram shows up he must defend his terf.