Picture Courtesy of: Veggie Tales: Abe & the Amazing Promise
What was the name of Abraham's wife, and who was the young concubine who gave birth to his son, Ishmael? Also, who was Ishmael's brother?
Abraham's wife was Sarah. In Sarah's insecurities, she gave her husband her Egyptian slave girl, Hagar (as a wife...she wasn't a concubine. The scriptures say that Abraham married her…archaeological finds discovered that such was a common practice of the time.) to bear a son. Hagar gave birth to Ishmael. By the time that Sarah (finally) became pregnant with Isaac, Ishmael was 14.
So Isaac & Ishmael were 1/2 brothers, for they had the same dad, but different mom. Technically speaking, Hagar was Isaac's step-mom, and Sarah was Ishmael's step-mom.
Ishmael was the first born son, and also very much loved by Abraham. But Ishmael was born out of Sarah’s impatience of having a child...Ishmael was not the son who God had "Promised" to Abraham. That's where the confusion often comes in with the Muslims.
Wanna see something neat though? Esau (Jacob's brother, of Isaac's 2 sons) married Ishmael's daughter (his cousin). So if Jacob hadn't "tricked" Isaac into giving him the blessing, and Esau had gotten it instead, then by marrying Ishmael's daughter, Ishmael would've had a piece of the blessing after all.