How many children did the Virgin Mary have?

Just one. Any children after that were born to just plain Mary.

Just 1 apparently.

I am guessing she was just plain old Mary after her first

We don’t know for sure, but Mary and Joseph had at least 4 sons after Jesus was born.
James, Joses (short for Joseph Jr.), Simon, and Judas called Jude.

More then One.. Jesus had half Brothers and Sisters.. And she was only a virgin with Jesus..

Three