no, Joseph could have been a widower; brother could mean close relative, etc.
Pure speculation. The fact is that the scriptures refer to Jesus' brothers and sisters and nothing in scripture suggests that Mary remained a "perpetual" virgin. Indeed, the passage wherein her virginity is mentioned clearly suggests that she did not know Joseph until AFTER Christ was born.
The chances are that if Mary were espoused to Joseph while she was a virgin, that Joseph would have been a virgin as well. Why is it that the Catholic Church doesn't bother to honor the Virgin Joseph?