Firstborn Son

What does it mean that Joseph “took to himself his wife” (Matthew 1:24)?
They held a wedding feast and then moved into his house, but did not consummate their marriage during the wedding feast as is typically done (see Bride and Bridegroom).

Then why is Mary still identified as his “betrothed” (Luke 2:5) wife when they traveled together to Bethlehem months later?
Betrothed wife became wife after the marriage has been consummated through sexual intercourse. Without already having held a marriage feast and living together, traveling together as a couple would have been unthinkable, and Mary having a baby, even more so.

Why does Matthew 1:25 say Joseph “did not know” Mary until she had given birth to her firstborn Son (Matthew 1:25)?
Throughout the Bible, to “know” is often used to indicate sexual intercourse: “Adam knew Eve his wife, and she conceived and gave birth to Cain, ...” (Genesis 4:1); “Cain knew his wife, and she conceived and gave birth to Enoch, ...” (Genesis 4:17); etc.

What do the words “until” and “firstborn Son” (Matthew 1:25) indicate?
Joseph not having had sex with Mary “until” she gave birth to υιον αυτης τον πρωτοτοκον (huion autes ton prototokon), the original Greek phrase that literally means “the firstborn son of her,” means that Joseph did have sexual intercourse with his wife after she gave birth to Jesus (see Jesus' brothers).

Then why do some people claim that Mary remained a virgin all of her life?
They think it helps them deify her and make it easier for people to worship and pray to her.

Why would anyone want people to worship Mary?
If Satan pointed to a dog and told people to worship it, most would laugh it off. But if he points to someone who was close to Jesus, like Mary or Peter, and tells people to worship them, some lend a ear.

As what does worshiping Mary or any other created being in the Bible qualify?
Idolatry.

Can people at least pray to Mary and have her petition God on their behalf?
No, Jesus told us to pray in His name directly to God the Father (see Ask and you shall receive).

What if I don't feel like I have a relationship with God the Father that warrants praying directly to Him?
Click here.