Born Again - Into the Family of God - Made Sons / Heirs with the Firstborn

Jesus answered and said to him, Truly, truly, I say to you, Unless a man is born again, he cannot see the kingdom of God.  

John 3:3

But as many as received Him, He gave them the authority to become children of God, to those who believe in His name; 

who were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God.

 John 1:12,13

Therefore, if anyone is in Christ, he is a new creation; the old things passed away; behold, all things have become new. 

And all things are of God, who reconciled us to Himself through Jesus Christ,

2 Corinthians 5:17, 18a

For you did not receive the spirit of bondage again unto fear, but you received the Spirit of adoption by whom we cry out, "Abba, Father."

The Spirit Himself bears witness with our spirit that we are children of God.
And if children, then heirs--heirs of God and joint heirs with Christ, if indeed we suffer together, so that we may also be glorified together. 

Romans 8:15-17

Because whom He foreknew, He also predestined to be conformed to the image of His Son, that He might be the firstborn among many brothers.

Moreover whom He predestined, these He also called; and whom He called, these He also justified; and whom He justified, these He also glorified

Romans 8:29,30

But when the kindness and the love of God our Savior toward man appeared,

not by works of righteousness which we did, but according to His mercy He saved us, through the washing of regeneration and renewing of the Holy Spirit,
whom He poured out on us richly through Jesus Christ our Savior,
 that having been justified by His grace we might become heirs according to the hope of eternal life.

Faithful is this word, and concerning these things I want you to strongly affirm, so that those who have believed in God may take thought to maintain good works. These things are good and profitable to men.

Titus 3:4-8

For it was fitting for Him, on account of whom are all things and through whom are all things, in bringing many sons to glory, to perfect the Author of their salvation through sufferings.
For both He who sanctifies and those who are being sanctified are all of one; for which reason He is not ashamed to call them brothers,

Hebrews 2:10,11 

* Jesus Christ is the first born Son, of many son's.

The Gospel of John points out that Jesus is the Only Begotten Son in the beginning 

became flesh and dwelt among us, and we beheld His glory, the glory as of the only begotten of the Father

( John 1:14 )

And after His crucifixion / resurrection, we ( His brethren ) are referenced as part of the same family ( same father ).

 Jesus said to her, "... go to My brothers and say to them, 'I am ascending to My Father and your Father, and to My God and your God.' "

John 20:17 

Therefore we can "rejoice" in the knowledge that we  ( all the brethren - believers ) have been "born again" into God's family,

and that we can ( should ) call / think of God as "our Father" ( and His Great Love for us ).

The better you can understand ( know as a fact ) this new relationship,

the stronger your faith ( confidence ) in what God has done for you, the easier your "burden".

Take My yoke upon you and learn from Me, for I am gentle and lowly in heart, and you will find rest for your souls.
For My yoke is easy and My burden is light."

Matthew 11:29, 30

 

And you can find "rest" in this knowledge ( your secure relationship and all that God has already done for you IN CHRIST ).

Therefore, a promise being left to enter into His rest, let us fear lest any of you should seem to come short of it. 
For also we have had the gospel preached, as well as them. But the Word preached did not profit them, not being mixed with faith in those who heard it. 
For we who have believed do enter into the rest, 
Since then it remains that some must enter into it, and since they to whom it was first preached did not enter in because of unbelief, 

Hebrews 4:1-3a,6