To understand Matthew 1:25, we can read it in context with Matthew 1:24.
I will quote the Interlinear (Greek) bible as follows for Matthew 1:24-25:
24 And being aroused from sleep, Joseph did as the angel of the Lord commanded him, and took his wife;
25 and did not know her until she bore her son, the Firstborn. And he called his name Jesus.
The Greek definitions of the following words taken from the above two verses are listed as follows with the Concordance cross-reference numbers so you can also check them if you wish.
aroused (1326) means: to awaken from sleep
took (3880) means: taking a wife.
know (1097) means:The verb is used to convey the thought of connection or union, as between man and woman.
bore (5088) means: to bring forth
My understanding of the verses using the original Greek translation is as follows:
24 After Joseph was awakened from his sleep, Joseph did what the angel of the Lord commanded him to do, and married Mary.
25 And he did not have sexual intercourse with her until she had given birth to her Firstborn son, who Joseph named Jesus.
The NIV version confirms my rough translation as follows:
“When Joseph woke up, he did what the angel of the Lord had commanded him and took Mary home as his wife. But he did not consummate their marriage until she gave birth to a son. And he gave him the name Jesus.”
Matthew 1:24-25 NIV
But the Catholic version is worded differently.
“Then Joseph, arising from sleep, did just as the Angel of the Lord had instructed him, and he accepted her as his wife. And he knew her not, yet she bore her son, the firstborn. And he called his name JESUS.”
Matthew 1:24-25 CPDV
The Catholic version is incomplete and as a result is misleading.
The words ‘And he knew her not…‘ in the Catholic version incorrectly implies that Joseph did did not have sex with Mary ever. Then she had a child called Jesus.
However, the original Greek and NIV versions indicate that Joseph did not have sexual intercourse with Mary before Jesus was born. It doesn’t say that she didn’t have sex after Jesus was born. In fact, according to the Bible, Mary had at least 6 other children. That is a big difference from the Catholic version. The Catholic version seems to be trying very hard to keep Mary a virgin her entire life which is not what the original Greek scripture actually says. I can see the Catholics using their misleading version of this verse to reject the fact that Jesus had four brothers and at least two sisters (Matthew 13:55-56 NIV, Mark 6:3).
On the contrary, the Original Greek also indicates that these 4 brothers and 2 or more sisters were “children from the same mother” as Jesus. From the definition of the word ‘brothers’ in the original Greek it is clear that Mary was their mother.
It is so important to go right to the original Greek or Hebrew in order to properly understand what the Bible is actually saying to avoid misinterpretation.