Abraham took a second wife after Sarah died: Keturah, a former concubine. Keturah was the mother of Midian (the father of the Midianites). Daughters, if there were any, weren’t listed.
Keturah was also the grandmother of boys named Sheba and Dedan, but these are not believed to be the founders of those two nations. A Sheba and Dedan from several generations earlier, the great-great-great-great grandsons of Ham, Noah’s son, have that honour.
Taking care to preserve Isaac’s future, Abraham saw that Keturah’s sons were provided for then sent far away before he died:
Genesis 25:5-6 Abraham gave everything he owned to his son Isaac. But before he died, he gave gifts to the sons of his concubines and sent them off to a land in the east, away from Isaac.