The Mystery of Cain

4:1 And the man knew Eve his wife; and she conceived, and bare Cain, and said, I have gotten a man with `the help of' Jehovah. 4:2 And again she bare his brother Abel. And Abel was a keeper of sheep, but Cain was a tiller of the ground. 4:3 And in process of time it came to pass, that Cain brought of the fruit of the ground an offering unto Jehovah. 4:4 And Abel, he also brought of the firstlings of his flock and of the fat thereof. And Jehovah had respect unto Abel and to his offering: 4:5 but unto Cain and to his offering he had not respect. And Cain was very wroth, and his countenance fell. 4:6 And Jehovah said unto Cain, Why art thou wroth? and why is thy countenance fallen? 4:7 If thou doest well, shall it not be lifted up? and if thou doest not well, sin coucheth at the door: and unto thee shall be its desire, but do thou rule over it. 4:8 And Cain told 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. 4:9 And Jehovah said unto Cain, Where is Abel thy brother? And he said, I know not: am I my brother's keeper? 4:10 And he said, What hast thou done? the voice of thy brother's blood crieth unto me from the ground. 4:11 And now cursed art thou from the ground, which hath opened its mouth to receive thy brother's blood from thy hand; 4:12 when thou tillest the ground, it shall not henceforth yield unto thee its strength; a fugitive and a wanderer shalt thou be in the earth. 4:13 And Cain said unto Jehovah, My punishment is greater than I can bear. 4:14 Behold, thou hast driven me out this day from the face of the ground; and from thy face shall I be hid; and I shall be a fugitive and a wanderer in the earth; and it will come to pass, that whosoever findeth me will slay me. 4:15 And Jehovah said unto him, Therefore whosoever slayeth Cain, vengeance shall be taken on him sevenfold. And Jehovah appointed a sign for Cain, lest any finding him should smite him. 4:16 And Cain went out from the presence of Jehovah, and dwelt in the land of Nod, on the east of Eden. 4:17 And Cain knew his wife; and she conceived, and bare Enoch: and he builded a city, and called the name of the city, after the name of his son, Enoch. 4:18 And unto Enoch was born Irad: and Irad begat Mehujael: and Mehujael begat Methushael; and Methushael begat Lamech. 4:19 And Lamech took unto him two wives: the name of the one was Adah, and the name of the other Zillah. 4:20 And Adah bare Jabal: he was the father of such as dwell in tents and `have' cattle. 4:21 And his brother's name was Jubal: he was the father of all such as handle the harp and pipe. 4:22 And Zillah, she also bare Tubal-cain, the forger of every cutting instrument of brass and iron: and the sister of Tubal-cain was Naamah. 4:23 And Lamech said unto his wives: Adah and Zillah, hear my voice; Ye wives of Lamech, hearken unto my speech: For I have slain a man for wounding me, And a young man for bruising me: 4:24 If Cain shall be avenged sevenfold, Truly Lamech seventy and sevenfold. 4:25 And Adam knew his wife again; and she bare a son, and called his name Seth. For, `said she', God hath appointed me another seed instead of Abel; for Cain slew him. 4:26 And to Seth, to him also there was born a son; and he called his name Enosh. Then began men to call upon the name of Jehovah.

Genesis 4:1-26 ASV

I believe that Cain and Abel were twins.

The reason that Cain's offering was not accepted was that he brought forth of the ground which had been cursed Abel ust have learned what happen in the garden of Eden and seen where God covered his parents with animal skins and seen that it was Animal sacrifices that pleased God not cursed offerings.

Cain premeditated to kill Abel and did.

Cain either took a cousin or sister or maybe ther were other people I don't know.

If it was a family member the gene pool would have been pure eneough to not have birth defects I would think.

Whether Cain's own family would have killed him or other people is up for debate.

When he was sent East of Eden into Nod That would be the deserts of Israel and the Middle East.

He has children then vanishes or does he?

4:23 And Lamech said unto his wives: Adah and Zillah, hear my voice; Ye wives of Lamech, hearken unto my speech: For I have slain a man for wounding me, And a young man for bruising me: 4:24 If Cain shall be avenged sevenfold, Truly Lamech seventy and sevenfold.

Genesis 4:23-24 ASV

This verse appears out of nowhere unless you know where to do the research.
The "Book of Gasher "which is mentioned in the Bible in Josh10:12-13 and2Sam 1:17-27.
It is considered in Jewish faith to be accurate it was lost for centuries then rediscovered.

The Bible does leave some questions unanswered or so it seems.
With the guidance of the Holy Spirit you find these things out.

I to read the oter books of the Bible and take stock in some of them.

And it was in the hundred and thirtieth year of the life of Adam upon the earth, that he again knew Eve his wife, and she conceived and bare a son in his likeness and in his image, and she called his name Seth, saying, Because God has appointed me another seed in the place of Abel, for Cain has slain him.
And Seth lived one hundred and five years, and he begat a son; and Seth called the name of his son Enosh, saying, Because in that time the sons of men began to multiply, and to afflict their souls and hearts by transgressing and rebelling against God.
And it was in the days of Enosh that the sons of men continued to rebel and transgress against God, to increase the anger of the Lord against the sons of men.
And the sons of men went and they served other gods, and they forgot the Lord who had created them in the earth: and in those days the sons of men made images of brass and iron, wood and stone, and they bowed down and served them.
And every man made his god and they bowed down to them, and the sons of men forsook the Lord all the days of Enosh and his children; and the anger of the Lord was kindled on account of their works and abominations which they did in the earth.
And the Lord caused the waters of the river Gihon to overwhelm them, and he destroyed and consumed them, and he destroyed the third part of the earth, and notwithstanding this, the sons of men did not turn from their evil ways, and their hands were yet extended to do evil in the sight of the Lord.
And in those days there was neither sowing nor reaping in the earth; and there was no food for the sons of men and the famine was very great in those days.
And the seed which they sowed in those days in the ground became thorns, thistles and briers; for from the days of Adam was this declaration concerning the earth, of the curse of God, which he cursed the earth, on account of the sin which Adam sinned before the Lord.
And it was when men continued to rebel and transgress against God, and to corrupt their ways, that the earth also became corrupt.
And Enosh lived ninety years and he begat Cainan;
And Cainan grew up and he was forty years old, and he became wise and had knowledge and skill in all wisdom, and he reigned over all the sons of men, and he led the sons of men to wisdom and knowledge; for Cainan was a very wise man and had understanding in all wisdom, and with his wisdom he ruled over spirits and demons;
And Cainan knew by his wisdom that God would destroy the sons of men for having sinned upon earth, and that the Lord would in the latter days bring upon them the waters of the flood.
And in those days Cainan wrote upon tablets of stone, what was to take place in time to come, and he put them in his treasures.
And Cainan reigned over the whole earth, and he turned some of the sons of men to the service of God.
And when Cainan was seventy years old, he begat three sons and two daughters.
And these are the names of the children of Cainan; the name of the first born Mahlallel, the second Enan, and the third Mered, and their sisters were Adah and Zillah; these are the five children of Cainan that were born to him.
And Lamech, the son of Methusael, became related to Cainan by marriage, and he took his two daughters for his wives, and Adah conceived and bare a son to Lamech, and she called his name Jabal.
And she again conceived and bare a son, and called his name Jubal; and Zillah, her sister, was barren in those days and had no offspring.
For in those days the sons of men began to trespass against God, and to transgress the commandments which he had commanded to Adam, to be fruitful and multiply in the earth.
And some of the sons of men caused their wives to drink a draught that would render them barren, in order that they might retain their figures and whereby their beautiful appearance might not fade.
And when the sons of men caused some of their wives to drink, Zillah drank with them.
And the child-bearing women appeared abominable in the sight of their husbands as widows, whilst their husbands lived, for to the barren ones only they were attached.
And in the end of days and years, when Zillah became old, the Lord opened her womb.
And she conceived and bare a son and she called his name Tubal Cain, saying, After I had withered away have I obtained him from the Almighty God.
And she conceived again and bare a daughter, and she called her name Naamah, for she said, After I had withered away have I obtained pleasure and delight.
And Lamech was old and advanced in years, and his eyes were dim that he could not see, and Tubal Cain, his son, was leading him and it was one day that Lamech went into the field and Tubal Cain his son was with him, and whilst they were walking in the field, Cain the son of Adam advanced towards them; for Lamech was very old and could not see much, and Tubal Cain his son was very young.
And Tubal Cain told his father to draw his bow, and with the arrows he smote Cain, who was yet far off, and he slew him, for he appeared to them to be an animal.
And the arrows entered Cain's body although he was distant from them, and he fell to the ground and died.
And the Lord requited Cain's evil according to his wickedness, which he had done to his brother Abel, according to the word of the Lord which he had spoken.
And it came to pass when Cain had died, that Lamech and Tubal went to see the animal which they had slain, and they saw, and behold Cain their grandfather was fallen dead upon the earth.
And Lamech was very much grieved at having done this, and in clapping his hands together he struck his son and caused his death.
And the wives of Lamech heard what Lamech had done, and they sought to kill him.
And the wives of Lamech hated him from that day, because he slew Cain and Tubal Cain, and the wives of Lamech separated from him, and would not hearken to him in those days.
And Lamech came to his wives, and he pressed them to listen to him about this matter.
And he said to his wives Adah and Zillah, Hear my voice O wives of Lamech, attend to my words, for now you have imagined and said that I slew a man with my wounds, and a child with my stripes for their having done no violence, but surely know that I am old and grey-headed, and that my eyes are heavy through age, and I did this thing unknowingly.
And the wives of Lamech listened to him in this matter, and they returned to him with the advice of their father Adam, but they bore no children to him from that time, knowing that God's anger was increasing in those days against the sons of men, to destroy them with the waters of the flood for their evil doings.
And Mahlallel the son of Cainan lived sixty-five years and he begat Jared; and Jared lived sixty-two years and he begat Enoch.