They were of age, or married (they married very young in those days) lived in another place, whatever.
They would not have been exempt from the census. If they existed, they would have all gone together.
Luke 2:1-5 And it came to pass in those days, that there went out a decree from Caesar Augustus that all the world should be taxed.
(And this taxing was first made when Cyrenius was governor of Syria.)
And all went to be taxed, every one into his own city.
And Joseph also went up from Galilee, out of the city of Nazareth, into Judaea, unto the city of David, which is called Bethlehem; (because he was of the house and lineage of David:)
To be taxed with Mary his espoused wife, being great with child.
>>>>If Joseph had other older children, why didn’t they go with him and Mary to the mandatory census in Bethlehem?<<<<
>>>>They were of age, or married (they married very young in those days) lived in another place, whatever.<<<<
Any older kids would have claim to the throne of David and would invalidate Jesus’ rightful claim to the throne, and title - King of the Jews. The regal line united in both Joseph and Mary, and then to Jesus, their firstborn according to the flesh. Any religious tradition of Joseph having kids from a prior marriage would undermine God’s Word.