I’m Lutheran but she’s right that those references to brothers do not necessarily mean biological brothers.
See Genesis 14:14New King James Version (NKJV)
14 Now when Abram heard that his brother was taken captive, he armed his three hundred and eighteen trained servants who were born in his own house, and went in pursuit as far as Dan.
The “brother” it is talking about here is Lot. Lot is identified elsewhere as Abram’s nephew.
Not necessarily, of course. Since it was so along ago, it cannot be confirmed 100% that Jesus’s brothers and sisters mentioned in the Bible, were actually His brothers and sisters. But I tend to treat the Bible much as I do the US Constitution. I don’t read into it. I read it as it is written and treat it as it is written. Since Mary and Joseph were a happily married couple, it is not unreasonable that other children followed Jesus’s birth.