Abram & Sarai - Abraham & Sarah Part One

18 And we all, with unveiled face, continually seeing as in a mirror the glory of the Lord, are progressively being transformed into His image from [one degree of] glory to [even more] glory, which comes from the Lord, [who is] the Spirit 2 Corinthians 3:18 AMP

​For Zeb from Bob-Bob
To A Young Man of God, Blessed be the name of Jesus Christ by whom we have eternal life  #BeBoldBelieveBig

Your Question
Why in Genesis does Abraham and his wife keep going into kingdoms and saying they are just brother and sister?   Zeb 11/8/16

Part One: As a background
Brief outline of the life of Abraham
Take a look at the first part summarizing the chapters in Genesis that have to do with Abraham's life.   

Part Two: 2 Chapters you refer to in your question
Genesis Chapters 12 and 20 in two columns

Part Three: Below the 1st Song 
A Brief Commentary 
Man's Fallen Condition
God's Continued Love & Grace
Before the Law of Moses,
During the Law of Moses and finally
in the days of God's love shown in the birth, life, death, resurrection and ascension of Jesus to the full day. 

​PART ONE
Descendants of Noah - Shem, Ham & Japheth

Genesis 11
verse 10 These are the records of the generations of Shem [from whom Abraham descended]. Shem was a hundred years old when he became the father of Arpachshad, two years after the flood.

There were 9 generations from Shem and Abram was the tenth generation since the days of Noah. 

Noah - Shem - Arpachshad - Shelah - Eber - Peleg - Reu - Serug - Nahor - Terah - Abram, Nahor and Haran <-firstborn and was father of Lot

verse 31 Terah took Abram his son, and Lot the son of Haran, his grandson, and Sarai his daughter-in-law, his son Abram’s wife; and they went out together to go from Ur of the Chaldeans into the land of Canaan; but when they came to Haran [about five hundred and fifty miles northwest of Ur], they settled there.

Genesis 12 see Part Two

Genesis 13  
Abram and lot go their separate ways

Genesis 14
Abraham rescues Lot and defeats 4 enemy kings and kingdoms and rescues 5 'friendly' ally kingdoms and takes the spoil of victory with 318 men! It was lot, his nephew that was his motive for asking and finding divine deliverance. Then Melchizzadek, King and high Priest  of Salem appeared bringing Bread & Wine and Abraham responded by 'tithing' 1/10th of all the spoils of war and did war no more! From then on The Lord dd all the judgment and warfare - from heaven! He intervened with dreams, angels, visions and other supernatural revelations blessing those who blessed his family and brought destruction on those who refused him or his people. In Abrahams life and the life of his sons, Isaac and Ishmael and Jacob and Esau we see the honor of god for the people He loves by covenant or agreements until the days of Moses, David, ELijah and the 1st Coming of the Word made Flesh - God become man giving Him the name Jesus!

http://www.communionfire.com/blog/first-mention-of-the-elements-in-communionfire-part-iii-then-melchizedek-brought-out-bread-wine

Abram and Melchizedek

17 Then after Abram’s return from the defeat (slaughter) of Chedorlaomer and the kings who were with him, the king of Sodom went out to meet him at the Valley of Shaveh (that is, the King’s Valley).

18 [c]Melchizedek king of Salem (ancient Jerusalem) brought out bread and wine [for them]; he was the priest of [d]God Most High. 19 And Melchizedek blessed Abram and said,

“Blessed (joyful, favored) be Abram by God Most High,
Creator and Possessor of heaven and earth;

20 And blessed, praised, and glorified be God Most High,
Who has given your enemies into your hand.”
And Abram gave him a tenth of all [the treasure he had taken in battle].

Genesis 15
God Promises Abraham  son

Genesis 16
Barren, Sarah offers Hagar to have the promised son

Genesis 17
God creates the Covenant of circumcision to set apart Abraham's children from the rest of the world, begining with Ishmael and Abram becomes Abraham and Sarai becomes Sarah (the "ah" means the name of God so as to ratif the covenant of circumcision.)

Genesis 18
The Three Angels visit Abraham to announce that Sarah will give birth to the son God promised Abraham and to warn Abraham about the destruction of Sodom and Gomorrah; Abraham intercedes for Lot and his family. 2 angels go to rescue Lot and family and Abraham. Type of Jesus and foreshadow of angels and deliverance of God's family. 

Genesis 19 
Destruction of Sodom and Gomorrah, death of Lot's wife. Lot and his family relocate, daughters get him drunk and sleep with him and one gives birth to Moab father of the Moabites and the other daughter gives birth to Ben-Ammi, father of the Ammonites. Type of the last days

Genesis 20 see Part Two

Genesis 21
Isaac Born; verse 4 So Abraham circumcised his son Isaac when he was eight days old, just as God had commanded him. 5 Abraham was a hundred years old when his son Isaac was born. Shadow of the Covenanted people

Genesis 22
Isaac on Mount Moriah as type of Golgotha

Genesis 23
Death and Burial of Sarah as type of Mother Mary? (Isaac) 

Genesis 24
Bride (Rebekah) for Isaac as type of Bride of Christ, second coming and wedding feast of the Lamb  

​Genesis 25
​Abraham's Death and the children of Ishmael and Isaac