We do not have to dates and times they conceived these children nor do we need them.
We don't have their birth certificates nor do we need them as the NT is about Jesus.
We do however have numerous passages telling us these are the brothers and sisters of Jesus. The Greek, and context, make this clear to anyone who reads the Word.
Another way we know Mary had other children is through the Greek as used in Luke 2:7 describing Jesus as her firstborn...in the greek it is prototokon: first born, eldest.
That Jesus is not her only child is clear as Luke did not use monogene, meaning only, one of a kind, unique. Luke being a doctor and writing his account around 60AD would have known if she'd had other children or not. Same can be said for Acts written about a year later. The other Gospels were written in a time span that would enable them to determine if there were or were not other children.
Again....context is your key to understanding this topic. The plain, clear reading of the Word is there for anyone to see.
Paul identified James as the Lord's brother. I'm not going into the Greek again or what brother means.
Matthew kept her a virgin until Jesus was born.
After Jesus was born, Joseph and Mary engaged in marital relations...or SEX. We know this because he kept her a virgin until His birth. After that they had sex.
Matthew 12:46, Matthew 13:55-56; Luke 8:19; Mark 3:31; John 7:1-10, Acts 1:14; Galatians 1:19 make it crystal clear He had siblings.
These are not children from another marriage.
These are not Joseph's children from another marriage.
These are the children of Joseph and Mary.
The text is crystal clear Jesus had brothers and sisters and they are from Joseph and Mary.
It appears we will not reach agreement on this, so it is fruitless to continue this conversation. I will leave you with links to commentaries on Luke 2:7 and Galatians 1:19. The diverse and contradictory opinions expressed in these commentaries demonstrate that the belief that Mary had other children is not as crystal clear as you make it out to be.
https://www.studylight.org/commentary/luke/2-7.html
https://www.studylight.org/commentary/galatians/1-19.html