If Joseph had other older children, why didn’t they go with him and Mary to the mandatory census in Bethlehem?
If there were any, perhaps they were born in a different census area; and were of age, so they went there.
Once we get into the area NOT covered in Scripture; all KINDS of scenarios can be hypothesized.
Most, if not all, will be a waste of time.
But, Rome seems to like the method.
What can ya do?
They were of age, or married (they married very young in those days) lived in another place, whatever.