Hebrew or Aramaic used the same word for "brother", "half brother", and "cousin", so it does not prove that Mary had other children.
A more positive reference to perpetual virginity of Mary is in this prophecy:
2 And the Lord said to me: This gate shall be shut, it shall not be opened, and no man shall pass through it: because the Lord the God of Israel hath entered in by it, and it shall be shut(Ezechiel 44:2)
How about these??? Matt. 1:18 This is how the birth of Jesus came about. His mother Mary was pledged to be married to Joseph, but "before they came together", she was found to be with child through the Holy Spririt.
Matt. 1:25 But he had no "union" with her until she gave birth to a son. And he gave him the name Jesus.
John 2:12 After this he went down to Capernaum with his mother and brothers and his disciples. (Why mention both brothers and disciples if they were one and the same?)
Acts 1:14 They all joined together constantly in prayer; along with the women and Mary the mother of Jesus, and his brothers. (The previous verse mentions all the disciples..so again, why the specific distinction?)
Matt. 12:46 While Jesus was still talking to the crowd, his mother and brothers stood outside, waiting to speak with him.(His answer indicated that all his disciples were inside with him...verse 49.)
Luke 2:7 And she gave birth to her "firstborn", a son. She wrapped him in strips of cloth and placed him in a manger, because there was no room for them in the inn.
These passages from Holy Scipture are very plain...and this is the reason Mary did not have perpetual virginity. There is much written to indicate she had a very large family. There is nothing written to indicate she was forever a virgin. The only proof from your quarter is your tradition. Your tradition is lacking.
I am not a protestant! Never been one. Don't buy most of what they say either.