Ishmael
Ishmael was Abraham's son by using Hagar as the surrogate mother.
This was often done in the Mediterranean countries at that time.
Ishmael was not the promised child who was to come some years later via Sarah.
Background Reading:
Genesis 16:1-17:27
Hagar and Ishmael
16 Now Sarai, Abram's wife, had borne him no children. But she had an Egyptian maidservant named Hagar; 2so she said to Abram, "The LORD has kept me from having children. Go, sleep with my maidservant; perhaps I can build a family through her."
Abram agreed to what Sarai said. 3 So after Abram had been living in Canaan ten years, Sarai his wife took her Egyptian maidservant Hagar and gave her to her husband to be his wife. 4 He slept with Hagar, and she conceived.
When she knew she was pregnant, she began to despise her mistress. 5Then Sarai said to Abram, "You are responsible for the wrong I am suffering. I put my servant in your arms, and now that she knows she is pregnant, she despises me. May the LORD judge between you and me."
6 "Your servant is in your hands," Abram said. "Do with her whatever you think best." Then Sarai mistreated Hagar; so she fled from her.
7 The angel of the LORD found Hagar near a spring in the desert; it was the spring that is beside the road to Shur. 8 And he said, "Hagar, servant of Sarai, where have you come from, and where are you going?"
"I'm running away from my mistress Sarai," she answered.
9 Then the angel of the LORD told her, "Go back to your mistress and submit to her." 10 The angel added, "I will so increase your descendants that they will be too numerous to count."