if god could create adam and eve without mother and father, why did it need a mother to create jesus (his son)?

To provide the "advocate" for mankind who knew both deity and human experience, in order to plead our case, 1 John 2:1.

GOD (aka THE SPIRIT; John 4:24)) became "Son of MAN" with BLOOD (I Timothy 3:16; John 1:10) so HE could shed HIS BLOOD (Acts 20:28) to forgive us of our sins (I John 1:17) and now we no longer have to make animal sacrifices for forgiveness (Hebrews 10:12-14)!

Jesus pre-existed Mary - so Mary did not create Jesus.

Jesus needed to come to earth and have the whole human existance experience and be without sin - birth and gestastion is part of the human experience so Jesus needed a mother and Mary was chosen for that.

Gods plan of redemption was he became fully human and without sin and then died on the cross. Mary was needed to fulfill Gods plan, She obeyed and was highly favoured

Unlike any other human, Jesus lived in heaven as a spirit person before he was born on earth. (John 8:23) He was God’s first creation, and he helped in the creation of all other things. He is the only one created directly by Jehovah and is therefore appropriately called God’s “only-begotten” Son. (John 1:14) Jesus served as God’s Spokesman, so he is also called “the Word.” - Proverbs 8:22, 23, 30; Colossians 1:15, 16.
God sent his Son to earth by transferring his life from heaven to the womb of a virgin Jewess named Mary.

What was the purpose of the virgin birth?
God used the virgin birth to provide Jesus with a perfect human body so that Jesus could save mankind from sin and death. (John 3:16; Hebrews 10:5) God transferred Jesus’ life to the womb of Mary. Thereafter, God’s holy spirit evidently shielded the developing embryo from acquiring any imperfection.—Luke 1:35.
Jesus was thus born a perfect human, an equal to what Adam had been before he sinned. The Bible says of Jesus: “He committed no sin.” (1 Peter 2:22) As a perfect man, Jesus could pay the ransom to redeem humans from sin and death.—1 Corinthians 15:21, 22; 1 Timothy 2:5, 6.

Jesus is the New Adam and the Virgin Mary is the New Eve. Jesus is Son of God and Son of Mary. He is True God and True Man.

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 had 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; but he took on him the seed of Abraham. 
Wherefore in all things it behoved him to be made like unto his brethren, that he might be a merciful and faithful high priest in things pertaining to God, to make reconciliation for the sins of the people. 

To fulfill prophecy.

Why do you want to know?

I will dismiss your rudeness and answer for people who are respectful: may my words ricochet off your heart of stone and be planted in good soil.

In order for the law’s requirement of ‘a life for a life’ to be fulfilled, God the Son (not a created being) chose to become a man to trade His life for Adam’s life, to rescue Adam and all who were in Adam’s body from the wages of sin, which is death.

He was born of a virgin woman (not a child but a woman) to fulfill the promise that the seed of the woman will crush the head of Satan; two among 300 prophesies about His first advent. God did what He had to do to rescue us, heal us and to give us back the authority Satan received from us.

God can raise children for Abraham from the stones if HE wants: He doesn’t need any of us. Better beg for mercy before it’s too late. Your time is almost up.

Jesus had to be able to take part in Jewish religious rites. If he was not born then he could not have participated. Also he had to be tempted in all manner just as we are. So he had to be born in such a condition that his birth right was in question. It always was and no doubt that interfered with him being selected for a position of authority inside the Jewish religion at the time.

The writers thought the "virgin birth" nonsense would spice up their story, so they put it in It's all pure fiction.