It might interest you to know that I first learned that Jesus had brothers and sisters in a Bible study class taught by a Catholic priest in a Catholic church. When we were going through the Gospel passages mentioning Jesus’s brothers and sisters, the priest did not say, oh, that’s a typo, they meant to say cousins, or here’s another whopper-—oh, they were Joseph’s children from a prior marriage. Nope. None of that. The priest put no spin on it at all. He simply taught the Bible as it written. Pure and simple. I was taught in the Church that Jesus had brothers and sisters by a Catholic priest no less.
I had NO idea that Father Martin Luther taught this late in history...oh well, see what happens when you make up your own rules...