see updates below
Question~ 
"Why does Catholic doctrine state that Jesus had no brothers and sisters and Mary was a lifelong virgin"

God says
"Is not this the carpenter's son? is not his mother called Mary? and his BRETHREN, James,  and Joses, and Simon, and Judas? And his SISTERS, are they not all with us? Whence then hath this man all these things?" Matthew 13:55-56

This verse confirms people in Jesus' home town that watched Jesus grow up from a young man helping His father in his trade as a carpenter, to doing great miracles right before their eyes. They remembered Jesus lived there as well as the fact that He had four brothers. PLUS they still have Jesus' SISTERS living among them. How many sisters did Jesus have? The Bible doesn't say. Why are they still living there? Did they get married and settled down in their home town to raise a family? It makes no difference. The fact is the Bible accurately records that Mary had many children.

Now yes, many claim that Joseph was was widowed and had children from a previous marriage. But if that was true, when Joseph and Mary went to Bethlehem to pay the new tax levied on all by Rome, why is it only Mary and Joseph traveled to Bethlehem? If Joseph had previous children he was required by law to bring those children with him so as to be counted in the census as well as be taxed.

Plus, when Joseph was instructed by the angel to flee to Egypt, no other children are mentioned at all. Notice what it says here in Matthew 2:13-14, "And when they were departed, behold, the angel of the Lord appeareth to Joseph in a dream, saying, Arise, and take the young child and his mother, and flee into Egypt, and be thou there until I bring thee word: for Herod will seek the young child to destroy him. When he arose, he took the young child and his mother by night, and departed into Egypt:"

God says
"While he yet talked to the people, behold, his mother and his BRETHREN stood without, desiring to speak with him. Then one said unto him, Behold, thy mother and thy BRETHREN stand without, desiring to speak with thee. But he answered and said unto him that told him, Who is my mother? and who are my BRETHREN? and he stretched forth his hand TOWARD HIS DISCIPLES, and said behold my mother and my BRETHREN!" Matthew 12:46-49

 Many teachers of Catholic doctrine believe that Jesus called only those that believed in Him His brethren. Did you notice the statement made to Jesus BEFORE He calls all in the room His brethren. A person comes to Jesus to tell Him that His mother and brethren are out side waiting on Him. Jesus took this opportunity to illustrate to the believers (disciples) and apostles in the room that THEY are considered brethren now because they believe in Him. Jesus actually says in Matthew 19:29  "And every one that hath forsaken houses, or brethren, or sisters, or father, or mother, or wife, or children, or lands, for my name's sake, shall receive an hundredfold, and shall inherit everlasting life." This verse is for believers that have to deal with unbelievers close to them. Does this verse not show Jesus calling those people that are not believers BRETHREN as well? It is no different than today, people from all walks of life call there fellow man brothers or sisters. What of the term, brothers in crime? And yes, just like back then, we have brothers and sisters in Jesus. Just because Jesus explained that if they believe in Him they become His brethren, does not say that Jesus denied His siblings. He just gained more brethren on this day.

God says 
"And when they were come in, they went up into an upper room, where abode both Peter, and  James, and John, and Andrew, Philip, and Thomas, Bartholomew, and Matthew, James the son of  Alphaeus, and Simon Zelotes, and Judas the brother of James. These all continued with one  accord in prayer and supplication, with the women, and Mary the mother of Jesus, and WITH HIS BRETHREN."  Acts 1:13-14

These verses are now calling the Apostles by name, and then Mary the mother of Jesus with His brethren are now mentioned. Are not all in the upper room Brethren? Yes they are, it's just illustrated here that Jesus' Mother and siblings are in the room as well. What better way to illustrate the fact that Jesus has an earthly family as well as His Church family. Think about it, all the Apostles are mentioned by name, THEN Mary and the BRETHREN of Jesus are mentioned. Is this an attempt to show the two types of brethren? Indeed it is.

God says
"After these things Jesus walked in Galilee: for he would not walk in Jewry, because the Jews sought to kill him. Now the Jews' feast of tabernacles was at hand. His brethren therefore said unto him, Depart hence, and go into Judaea, that thy disciples also may see the works that thou doest. For [there is] no man [that] doeth any thing in secret, and he himself seeketh to be known openly. If thou do these things, shew thyself to the world. For neither did his brethren believe in him.
John 7:1-5

This I must concede is my favorite verse on this subject. How can it not be realized that "His brethren" here is BLUNTLY speaking of siblings? The argument is mute for those that would claim, "brethren" = "disciple" as well. How? The BRETHREN in this passage are telling Jesus to be on His way and go perform His miracles so that His "DISCIPLES" will see it "For neither did his brethren believe in him."

God says
"But other of the apostles saw I none, save James THE LORD'S BROTHER."  Galatians 1:19

How blunt can you get? Is this not an obvious verse? We found earlier in Matthew 13:55 that one of Jesus' brothers was named James, and here we see James is mentioned again as The Lord's Brother. By the way, this is the same James that was inspired by God to write the book of James in the New Testament.

God says
"And he knew her not till she had brought forth her FIRSTBORN son: and he called his name  JESUS."  Matthew 1:25

Did you notice that the Bible calls Jesus the firstborn son of Mary? Why would the infallible Word of God call Jesus the Firstborn if He is supposed to be the last-born, as well as the one and only son of Mary? According to Catholic doctrine this can't be. But I ask, how can Catholic doctrine call Mary a virgin until death when the Bible states the exact opposite numerous times? Notice the word "till" in the above verse? The verse preceding this one tells us that "Joseph being raised from sleep did as the angel of the Lord had bidden him, and took unto him his wife: And knew her not till she had brought forth her firstborn son:" [Matthew 1:24,25] It seems rather plain. Joseph went ahead and did as the Angel told him to and married Mary. Then we see the Bible tells us Joseph "waited" to consummate the marriage "till she had brought forth her firstborn son" This easily proves Mary was no virgin. It is easy to say that her "firstborn" actually means she had MORE. And that declares openly that she had children other than Jesus..

On more obvious note to ponder...

As blessed and loved as Mary was of God, do you honestly believe that the Almighty and ever living God of all creation would punish her with a barren womb after submitting to His perfect will without question and having His Son? Remember that it was considered a blessing to have children back then, unlike today's society with their millions of self centered flesh pleasing abortions.  PLUS, would it not be considered sin on Mary's part to DENY Joseph's carnal desires towards his wife? Is it not written.. 1 Corinthians 7:3-5, "Let the husband render unto the wife due benevolence: and likewise also the wife unto the husband.  The wife hath not power of her own body, but the husband: and likewise also the husband hath not power of his own body, but the wife.  Defraud ye not one the other, except it be with consent for a time, that ye may give yourselves to fasting and prayer; and come together again, that Satan tempt you not for your incontinency."


UPDATES:


 

 

Truth is truth

.

Presents of God ministry