Almost everyone knows the story of Cain and Abel. They were the sons of Adam and Eve. Abel was a keeper of sheep, and Cain tilled the ground. When it came time for the brothers to bring their offerings to God, Abel brought one of the first of his lambs and it was accepted. However, Cain brought his fruit of the ground as his offering, and it wasn't accepted. It wasn't what God had specified, so Cain got angry. "8 And Cain talked with Abel his brother: and it came to pass, when they were in the field, that Cain rose up against Abel his brother, and slew him. 9 And the Lord said unto Cain, Where is Abel thy brother? And he said, I know not: Am I my brother's keeper?" Genesis 4:8-9 KJV The rest of the story is how Cain became a fugitive, so to speak, but God put a mark on him so no one would harm him.
But do you know the story of Isaac and Ishmael? They were also two brothers: one of whom was full of animosity towards the other. They had the same father, but different mothers. Their father was Abraham, who was known as the forefather of the Jewish nation. Ishmael was his firstborn from his wife's Egyptian servant, because Abraham and Sarah got impatient waiting for God to make good on his promise to give them a son. God had told Sarah that she would be a "mother of nations" but she didn't believe Him. So...she was 90 when she finally did give birth and Abraham was 100, as God made them wait 25 years for their unbelief.
Unfortunately, Ishmael did not like his young brother and was mean to him. Sarah saw this and said to her husband, "Cast out this bondwoman and her son: for the son of this bondwoman shall not be heir with my son, even with Isaac. And the thing was very grievous in Abraham's sight because of his son. And God said unto Abraham, Let it not be grievous in they sight because of the lad, and because of they bondwoman; in all that Sarah hath said unto thee, hearken unto her voice; for in Isaac shall thy seed be called. And also of the son of the bondwoman will I make a nation, because he is thy seed. And Abraham rose up early in the morning, and took bread, and a bottle of water, and gave it unto Hagar, putting it on her shoulder, and the child, and sent her away: and she departed, and wandered in the wilderness of Beersheba." Genesis 21:10-14 KJV.
Don't feel bad for Ishmael. "And God heard the voice of the lad; and the angel of God called to Hagar out of heaven, and said unto her, What aileth thee, Hagar? fear not; for God hath heard the voice of the lad where he is. Arise, lift up the lad, and hold him in thine hand; for I will make him a great nation." Genesis 21:17-18 KJV.
Until several years ago I had wondered if the two brothers ever reunited. I got my answer when I came across this passage: "Then Abraham gave up the ghost, and died in a good old age, an old man, and full of years; and was gathered to his people. And his sons Isaac and Ishmael buried him in the cave of Machpelah, in the field of Ephron the son of Zohar the Hittite, which is before Mamre." Genesis 25:8-9 KJV. They came together to bury their father. And that's pretty much the last we hear of Ishmael, yet not Isaac. So it isn't as if they reunited because of a familial bond.
You may be asking yourself 'so what makes them worse than Cain and Abel'? Well, remember how each one was going to be the father of a nation? Isaac was the father of the Jewish nation, while Ishmael was the father of Islam. And that kind of sums it up, and explains the animosity between those two nations: even to this day. It's amazing what you can discover when you read the Bible and do some research.
Have a blessed day.