They summoned the goddess Yogamaya and had her transfer the fetus through the womb of Devaki towards the womb of Rohini (Vasudeva's other spouse who lived along with her sister Yashoda across the river Yamuna, from the village of cowherds at Gokulam). Therefore the child conceived in a single womb https://f004.backblazeb2.com/file/DigitalAsset/SouthernCaliforniaSurrogacy/Becoming-A-Surrogate-In-Southern-California.html