Scripture actually mentions Jesus' brothers and sisters, Rhi - even nanes a few.
Note that the words aren't 'step-brothers' or 'half-brothers'' phrases for which existed in Hebrew, Armaic and Greek, but which are not employed in the Gospels.
So I'm arguing from a Scriptural, rather than a traditional, pov here.
Of course, even if Scripture hadn't mentioned them, Mary and Joseph going on to have a few other children would take absolutely nothing away from Jesus being, as Christians believe, God Incarnate.