Balram, elder brother of Sri Krishna, are found in the Srimad Bhagavad Purana, Mahabharat and Hari Vamsa. Balram has two mothers – Devaki and Rohini. Balarama was born in the womb of Devaki. As Devaki was imprisoned and Kamsa had decided to kill all the children born to her, the child from the womb of Devaki was placed inside Rohini.
Devaki and Rohini were the wives of Vasudeva.
Even though Balram was born first in the womb of Devaki, his mother is Rohini as she delivered Him.
Balram is an incarnation of Adi Shesha.