The Hybrid [dual] nature of our Lord Jesus Christ
Jesus constantly resisted using His first nature to overcome sin

God is a mystery who reveals Himself to us individually for the asking

1. but His human part of Him is clearly revealed in the holy Scriptures for us to behold, and by beholding we become changed.
2. Jesus did not have the "experience" of Romans 7 in that He never did that which He would not, nor what He hated did He not.  He never sinned.
3. But He would have sinned if He had taken Peter's advice (Matthew 16:22) and evaded the cross.  Here is the sublime truth of the incarnation of our Saviour: In order to "condemn sin in the flesh", He needed the cross!  And so do we!  The cross was not His "saviour", but He needed the cross in order to be our "Saviour".

How could Jesus then be made like unto His Brethren? 

St. Paul is an example of a holy Brother: "I am crucified with Christ: nevertheless I live; yet not I, but Christ lives in me: and the life which I now live in the flesh I live by the faith of the Son of God, who loved me, and gave Himself for me." (Gal.2:20).
"Here is the patience of the saints: here are they that keep the commandments of God, and the faith of Jesus (the faith of the Son of God). (Revelation 14:12).

The heresy of the Immaculate Conception contradicts the true humanity of Jesus and overthrows the good news of salvation.  If Mother Mary is outside the camp where humanity is held captive by the Evil One, then the child which she has miraculously conceived will Himself also be born outside this camp, but thank God this is not the case:

"Forasmuch then as the children are partakers of flesh and blood, He also Himself likewise took part of the same; that through death He might destroy him that has the power of death, that is, the devil; and deliver them who through fear of death were all their lifetime subject to bondage
For verily he took not on Him the nature of angels [un-fallen ones]; but He took on Him the seed of Abraham".
Wherefore in all things it behoved Him to be made unto His brethren, that He might be a merciful and faithful high priest in things partaining to God, to make reconciliation for the sins of the people.
For in that He Himself suffered being tempted, He is able to succour them that are tempted." (Hebrews 2:12-14).

In all things made unto His brethren
Let us be careful not to make our Lord human all together!  Because Jesus was born of the Holy Spirit at birth, He had a head-start on us.
We as His brethren have to be born again or those born into the family of believers must also keep on walking in the Holy Spirit day by day and minute by minute.

Did Jesus have an advantage over us?
Just as Jesus was born of the Holy Spirit and walked in it, so are we to walk.  Only He had it much harder in that He had to constantly resist using His first nature and that at every step Satan opposed and annoyed Him.

Did you notice that He took the seed of Abraham?
(Heb2:16) and the seed of King David (Romans 1:3). in other words, not the un-fallen nature of Adam!

Summery:
There is no excuse for us to sin