My imprimatured Catholic Bible says clearly "brothers" and "sisters" and nothing about there being anything like "among his own kin" being omitted, which has no bearing on the meaning of the text anyway. What manuscript has that in it: Vaticanus B? Sinaiticus? or some other obscure corrupted text?
There is no footnote in my Catholic Bible that says that these brothers and sisters were anything other than what it says they were: brothers and sisters. And we both know that if they were not children of Mary, then they could not have been brothers and sisters of Jesus, right?
My priest calls us brothers and sisters. He's not my brother, nor am I related to anyone in the parish. Perhaps I should correct him next time?
Then Jesus said unto them, "Be not afraid: go tell my brethren that they go into Galilee, and there shall they see me." Matthew 28:10 KJV
Why did He call the Apostles "brethren?" Maybe because "brethren" and "brothers" means more than just siblings?