If His mother was so unimportant, as most Protestants would have us believe, and his brothers were so numerous then why would Jesus bother to say anything and why would it be in the Scriptures?
Actually, I'm not one to say his mother was unimportant. I believe his mother was very important.
However, IF we assume a (seeming) blood-brother relationship between Jesus and James and others, then we have limited choices.
Either Jesus shared one parent with those brothers OR he shared both parents with those brothers.