I’m sure He did have sisters. I suppose it was the culture at the time, but, when Jesus fed the 5000, He only counted the men, not the women and children. I’ve always felt also, that Jesus had brothers and sisters because God loves His creation. Told us to go and multiply and I don’t believe God would have left Mary without other children. Also, back then women didn’t have jobs, relied heavily on husbands and their children. Especially as they grew older.
Why did Jesus commend Mary to John's care as he was hanging on the cross, if she had other children to take care of her?
Yes, it would be strange indeed if Mary had one child, Jesus, at the age of 12 or 14 or however old she was, and then have no more children. Why would she ignore her maternal instincts (and human desires)? And Joseph could go for that? I don't think so. There is plenty of room for common sense in Christianity, and it is disappointing to see so many people prefer unnatural, weird science fiction.